>>21922844Hitmontop's a good doubles mon in general, but that's not because of Rapid Spin.
Here, take a look at this chart. It probably doesn't mean much to you, but still.
>>21922893Rotom-Heat is actually already a great partner for Torterra.
It resists all of Torterra's weaknesses and Torterra can sponge Rock-moves and deal with Water-types which are Rotom-H's biggest problems.