What lot venue should I use for roller/ice rinks?

if you set it to generic people won't go to your skating rink unless you bring them there. like, townies won't even generate on the lot to fill it up.

I would suggest either a park (if outdoors), the bar, or a lounge.

if you want eating to be a main focus of the venue (aside from the rink, obviously), I would not recommend setting it as a restaurant since the functions of the restaurant will take precedence over that of the skating rink. a bar or lounge would do just fine.