Trainer/Roller Activities:
-Single Leg Drills (example, 5x(30 sec. left, 30 sec. both, 30 sec. right, 30 sec. both) just in the middle of a ride)
-Spin Ups (i.e. I spin average cadence, but spin up to much higher cadence and shift up)
-Low Resistance/High Cadence (Favorite on the rollers: Ride 60 seconds at high cadence then 60-120 seconds of average cadence and repeat. I try to average a higher cadence each rep of the high cadence. For me, I can't sustain 140 for more than a few seconds, so I shoot for 140 avg. on the repeats and spin 100-110 avg. on the rest - which is where I do most of my riding).

Never done high resistance/low cadence. I've heard people recommending it. My knees start to hurt when I'm riding at <70 RPM on a hill though.

I noticed my biggest improvements after spending a week on the rollers and incorporating the first three activities I mentioned (a total of 120 minutes in 5 days, not huge, but more than I generally get to ride).