A lot of the more popular characters right now have very good rolls, or their rolls have additional utility beyond standard movement.
Little Mac relies on his amazing rolls to get him around on the ground and punish over-aggressive foes, as otherwise a grounded target is inherently an easier target than one in the air, and Little Mac does not want to be in the air if he can avoid it. Even if his dash speed is very high and his dash is very low to the ground, that does not change the fact that having one less dimension to move around in makes your movement more predictable. His amazing rolls help mitigate that significantly, which is why they get used so often.
Rosalina uses rolls a lot to keep a separated Luma from moving with her. Luma normally performs the same inputs as Rosalina, so if she dashes normally Luma will dash in the same direction. However, Luma lacks the ability to roll, so rolling is an easy way for Rosalina to manoeuvre without moving Luma as well, as well as a way to desync herself from Luma by having him perform an attack as she rolls. On top of that, her rolls have her go invisible for most of the roll, giving them mindgame potential against an inattentive — or preoccupied — opponent.