It's August and we're already having a February thread? Mods, where are you when we need you?
To the OP, there are really several different perspectives going on here, and you have to decide what your own perspective is.
Perspective 1: I want to sweat and hurt all winter to come out better and stronger than I was the summer before. It isn't supposed to be fun. It's supposed to improve me.
Perspective 2: I have to tolerate it. It's a long winter and I need some downtime anyway. Fahrtlek is a term very out of style right now, but it's basically LSD (long slow distance) and winter is a good time for that. Miles on the road -- another equivalent term.
Perspective 3: I know I'll lose conditioning, but I improve on the road (or on the track) and I'll do my serious training there. I'm just limiting the loss and want variety and so on to enjoy myself and not get fat.
Those who really love trainers, especially Kickrs, tend to be in the first camp. Google up the YouTubes of Chris Hoy on a trainer and that's what you want to be. He does an interval, then has a climber's crash pad next to him so he can literally fall off the bike in a fetal position and cry. He believes that every bit of training has to be 100% of what you are capable of, or you don't improve. It's hard to go outside and work that hard in cold weather -- whether it's icy patches on the road, or the cold, or the dark, or whatever, roadwork just doesn't give you that improvement. And in that "hard training makes for easy winning" philosophy, you work harder in the winter and win better in the summer.
Those who love rollers are a mixed bunch. (For full disclosure, by the way, I ride a Kickr (ride it hard) and also ride Trutrainer rollers quite a bit.) In an hour on the rollers one can get seriously dehydrated -- a fan blow some of the sweat off you but doesn't change how fast you sweat. I find you can burn quite a bunch of calories on rollers, as long as you are doing enough effort (I'm not talking about conversational pace here). But I find that roller workouts have a couple benefits. First, your legs tend to lose suppleness after a long season of racing. Rollers help recover some of that. Your legs have to learn how to get out of their own way, how not just to contract and push, but how to relax. Training at 140 rpm in an 81 inch gear on rollers doesn't suddenly make you fast at 120 rpm in a 92, but it does add one of the components that makes other kinds of training more effective. Plus, it's winter, and it's variety, and it does build smoothness and agility, and it does burn a fair number of calories. A great combined winter workout is cross plus rollers -- both workouts limber you up a bit and also teach rapid accelerations. Rollers do have their place, and I would use them if I just wanted some aerobic fitness and wanted to keep weight off. My goals are a bit different, though.
Bike work? Well, if it's -5 C outside, I know that no matter how much I bundle up, I won't be able to do the power workouts I probably should be doing. The rides are for social benefit and to get some alternate aerobic training in. I can't even say that cold weather is that good for riding a low-geared fixie -- I simply don't warm up enough to be talking about suppleness. By the time I wear enough layers to get the legs warm, that sure ain't supple.
The point here is that I'm working to build power for the track and for fast accelerations in crits and on the road -- I'll ride support for a team leader on the road and hope for the same support in turn on the track. I do lots of weight work -- heavy weight work -- through the winter, and after 4-6 weeks of that I'll transition to some really hard Kickr workouts for about the same period. I don't get completely bored by those durations, they are enough to get some measurable improvement, and then I just do some sustenance workouts in one mode while I'm concentrating on the other. I don't do both together because if I'm doing one of them hard enough, I won't be able to do the other one well enough. Color me stupid, but I'd rather work harder in the winter and get to work less in the summer -- then I stay more rested for when it counts. But is this the most pleasant way to train and race, and is it what my team mates all do so I'm always part of the big training ride family? Sadly, no.
You don't need a Kickr or TruTrainer rollers to train well. Frankly, any decent trainer does well. There's no gap at the bottom of the pedal stroke on trainers -- that's where you're weak and where the low resistance on rollers enables you to pedal through and feel it better. There's no particular physiological benefit to one trainer over the other as long as it's reliable and smooth (which actually cuts out many of them). I do think that for what Kreitlers cost, the basic TruTrainer (without the resistance flywheel) is a much better pair of rollers, but when folded it does leave the roller drums exposed, so it makes it harder to throw it in the back of the truck on the way to the track. Thus, I have both Kreitlers and TruTrainers, and the Kreitlers get the abuse away from home before a race. I can ride rollers reasonably well and think the eMotions are a waste of money and hardware. If you want to roll along and watch TV, maybe they are for you. I find they just trip my wheel and knock me over anyway, but mostly I just don't need the hardware assist -- I'm on there to do a job and I'm focused on it. As for the Kickr, I've tried it with all the different training programs but when it comes down to simple hard ugly intervals, I either use a basic interval timing program, or I just do it myself with the Kickr software on an iPad. If I'm concentrating enough on the workout, I'm not even aware of what music or TV show might be playing in the room. That's how a hard workout should be.
To the OP, you said you had a trainer and didn't seem to like it, and were considering roadwork versus rollers. I'd actually suggest that you combine them. And try adding some weight work as well. Even if you get a sandbag training bag (google "sandbag workouts" for plenty of products, and one of the better made ones is from Goruck) you can still do some good workouts with it, though I much prefer and recommend using free weights. All these things will help you. You can't do them all together and do them well, so focus on one or two, then rotate. It keeps you from getting as bored (or burned out) if you set yourself a 2-week goal, say, to get as much improvement as you can get from a trainer or from rollers, then move on and come back to that method in a month or two. You sound as though you do get bored when training in the winter, and you need achievable goals for the winter -- not too much roadwork because you never warm up again, not too much trainer work because it's hateful, not too much roller work, not too much weight work, and so on. If you have to do ten killing trainer workouts in two weeks and then not look at it for four weeks because you are rotating to rollers plus weights for two weeks, then to roadwork for two weeks, you're going to be a lot happier. It may not be absolutely the best training protocol for Hoy or Cancellara, but it may be the best for you. That's what counts.