Baal can you be a little more clear?
The owner should have general liability insurance with his insurance already, I'm fairly certain it'd be illegal to operate his business without it. Even if you take out the element of skating, let's say someone trips in the bathroom and sues. That's what general liability is for.
Unless your rink owner runs your league, your league needs their own general liability. This covers your skaters, fans at your bouts, etc. This is part of the WFTDA/MRDA insurance and is why everyone must be on the policy.
Does that help at all?