When a baby roll rat pops out, leave it on wondering because it will gather berries, feeding itself. As long as there are bushes it can access, and it can't escape its enclosure, it will raise itself making it one of the easiest tames to raise. All you have to do is imprint!
Great tame for getting around the map I would recommend taming one and using it to quickly run out of a rock drakes nest as it will help a tone in doing so due to the roll rats fast speed to turn into a rolling machine in turn too get this, 'roll' away it's a good all-around mount just be careful near ledges and you should be good to go!(Ps looks saggy bag of potatoes he/she is not hard to spot) he/she is also very territorial over his gems so steal them if you have 130% movement speed.