I've seen roller players in higher ranks, and they are usually very good. They use a combination of stealth and quick movement to get kills, which is the basic function of rollers in general. This game has not been kind to rollers however, I would not recommend using them in ranked unless you are a roller master, or your rank is low enough to where you can experiment comfortably.
My advice, don't focus much on inking turf by rolling around, swim with the ink your team is laying down, and stick close to someone. Once they start to engage an enemy, support them with an ambush of your own so long as you are close enough. If you are playing support, then you won't be directly engaging enemies much, but you can assist your teammates very well in combat. If there are no enemies around, maybe the enemy team got wiped out, then you can lay down ink, focus on the zone, put down beakons if you have the Krakon, etc.
For roller abilities, swim speed is the most important one you could equip. It allows you to swim and jump greater distances, and get up in your enemy's face for a quick splat. Ink recovery and ink saver main is always nice to have as well, since you go through ink very quickly if you are flicking a lot. If using the krakon for the beakons, having some sub saver would be wise as well.
As of right now, Zones is the best mode for the roller in my opinion. The focus on the middle allows for better uses of the beakons, since the action is not moving much unlike RM and TC. However, with TC, rollers work wonders on enemies who are moving the tower forward, so long as you approach carefully. RM is the mode I think is the most tricky for rollers, but it can still work so long as you are playing on a map that allows you to hide and splat passerby enemies. Humpback for example is pretty great in that regard.
As for which rollers to use, until things get balanced, the Splat roller and Krakon are the only reliable weapons. Dynamo rollers are just not what they used to be, (hooray!) the flingza roller's gimmick of the long range vertical flick will not help much since it takes too long to activate, and Carbon rollers, while better than the dynamo and flingza, are not as reliable for combat unlike the first game.
And while my beakons usually are not used much in turf, (much to my chagrin) anyone who has good knowledge about Splatoon will use and attack beakons in ranked. Maybe not the C or B ranks, but the higher you go, people will know just how important beakons are.
