Heatran is pretty much needed because you need a flash fire user on all sun teams so they dont counter sweep with fire moves lol. It also checks
[email protected] who are currently asses to your team (Heatran also wants Roar somewhere on its set or Sub CM Latias is an auto loss for any sun team). Roserade seems dead weight and overly redundant.
Also Roost (BW2 tutor) Should be over Morning Sun on Volc, its more reliable and has more pp.
Also Rash Nature and SuperPower > Focus Miss on Hydreigon (BW2 tutor). This guarantees a KO on non Chople Tar and also KO's Blissey and hurts Chansey and Heatran very badly.
Dugtrio is also needed on basically all sun teams imo. Mainly to remove counters like Tyranitar, Heatran and Blissey to your other sweepers from the match.
Dugtrio @ Focus Sash
252 Atk / 252 Speed / 6 Def
Trait: Arena Trap
- Substitute
- Hone Claws / Stealth Rock [ONLY use SR if you dont use it on Tran]
- Earthquake
- Stone Edge / Reversal
Wobbuffet is also acceptable and accomplishes much the same thing but wont remove Heatran as good as Dug. If you use Wob i suggest you find a place for EQ on Venusaur to revenge kill it.
Wobbuffet @ Leftovers
6 HP / 252 Def / 252 Sp.Def
Bold Nature
Trait: Shadow Tag
- Encore
- Mirror Coat
- Counter
- Safeguard
This should go over Volc or Hydreigon.
Forretress is a horribad Pokemon and should never be relied on for spinning because its absolutely the worst spinner in the game imo. It has 0 offensive presence to hurt ghosts or anything. Starmie is a much better spinner with a set of HP Fire/Psyshock/RS/Grass knot for sun teams as this set heavily damages ghosts. Sure you lose Spikes but i question their effectiveness because you have no anti spin yourself.
Hope this helps a little, good luck.