No only 'to roll', but also 'to slide' and 'to ride': кататься с горки, кататься на лошади / на велосипеде / на машине and even 'to glide' (e.g. using a row boat). Whatever kind of movement the verb denotes, it always implies doing it for pleasure as opposed to катиться which simply means 'to be rolling along' or 'to be sliding' in a certain direction.
Thanks. To clarify, if you were to just say, "Я катаюсь" with no context and nothing (no "на лыжах" / "на коньках") after it? That means either "I'm sliding" (like "I'm going down a playground slide") or "I'm rolling" (like "I'm physically turning myself over as a means of locomotion on the floor")? Surely for the riding meaning you'd have to specify what it is you were riding?
You should be careful with diminutives in -ка. For example, Oля to Oльга is like Pete to Peter, Олечка and Оленька are perceived as "Оля, dear", Олюшка - as "Оля, darling" or "honey", but Олька sounds very casual - almost like "Оля, you naughty girl" or "Oля, you old buddy". So -ка alone doesn't really add any endearment to a name, or, at least, to most Russian names. All it does is state a certain level of intimacy between people, but it will sound rude if applied to a stranger or a person of a lower social background or rank. Дочка is an exception, though, as it sounds very warm as opposed to дочь which is neutral if not a bit too formal