Hmmm... I tried to play a Leafeon/Roserade deck once, it didn't go that well xD. But anyway, in my deck I used a Landmin LvX and a Leafeon LvX. Add in an expert belt and your 90hp becomes 170hp. The only problem is that 2 LvX's could be a bit messy (especialy since there's only one you really want active). Personally, I would go with Shaymin LvX if you ever plan on bringing up a Roserade from the bench, but there's no reason not to include both cards you mentioned.
A thought that just occured to me just now is to run 4 RR Eevee's, 1 Espeon MD, 3 Leafeon UD and a Leafeon LvX. Eevee has a zero energy attack which allows you to search for 2 eeveelutions and put them in your hand (IIRC), Assuming you can get out 2 Eevee's asap, you should be able to get it to 110hp by turn 2. Once Leafeon LvX comes out, it becomes 130hp, and if you want to belt it you get a not so shabby 150hp.
The other advantages to Leafeon LvX (sorry I keep going on about Leafeon LvX) are that it's power allows you to attach 2 energies per turn (which goes well with Roserade), and it gives it a somewhat decent 2nd attack if you cant get the energy needed to ko an opponent for one turn