...Unfortunately, what I'm about to tell you is not possible in the update since Rhythm's abilities are being changed, but since this is the live game...

You will want to have as many high stat robots as you can on your team when you attempt to train any of the Support robots. An ideal place is Final Destination since you get full stat downloads when disabling a Robot Master. You should equip Roll with either the Swaps or the Shuffles that switch up Attack, Defense, or Speed, depending on which one you want to train. You already have the Roll Buster equipped, and that is good.

The idea is to switch the enemy stats with the stats of your trained robots so that Roll gets MANY points when disabling that robot. If Roll is unable to disable a robot normally with Buster Shot or a charged buster, use Roll Buster to bring the robot's defense down to 1. In that state, a single Buster Shot will do a TON of damage. I would recommend training Roll's speed first until she can always attack first under normal conditions (though do keep in mind some abilities like Quick Boomerang and Search Snake will move first regardless of whose speed is higher), then raise her other two stats.

Raise Attack first if you want Roll to deal more damage normally, though do be careful if the other robots get super high Attack, as they could knock Roll out in one blow. To prevent that, you can also train Roll's Defense first, and that might be the best way to go. You will have to use Roll Buster to break down the robot's defenses, but you will get the full Defense allowed with that disable.

This will take a while, but I was able to max out all of the Support robots using this strategy. Good luck!