Alright. Rating this upon request. First off, the massive offensive Volcarona weak has been pointed out by several raters. It can set up on Breloom, Jirachi, a weakened Latias, and Scizor. That's 2/3 of your team it can set up on already, and it can take out Jellicent by using Giga Drain or Heatran with Hidden Power Ground, leaving you with only one answer at worst and two answers at best. If you're dead set on running Roar over Earth Power on Heatran, then you could try using Toxic
over Will-O-Wisp on Jellicent, which can be used as set-up fodder by Volcarona under the sun. Toxic allows Jellicent to turn the tables on Volcarona, draining its HP and providing you with a solid win condition against it, no matter the time of battle, and this especially helps when Volcarona happens to be the last Pokemon in the opponent's party, in which case Roar from Heatran, assuming you've decided to use that, can't do jack to it. Besides, you already have Scald for that burn chance, and while having both Scald and Will-O-Wisp is reliable, covering Volcarona is more important IMO.
Now, I like Breloom, but I don't think it's doing too much for your team besides giving Volcarona and Mamoswine free opportunities to come in and take a chunk out of your team. You mentioned that you chose Breloom because it broke through bulky waters, so I'd recommend trying out a Nasty Plot Celebi
over your Breloom. While you may refuse this change, claiming that it just makes you weaker to Volcarona and Mamoswine, the change recommended in the previous paragraph covers Volcarona, and Celebi covers bulky waters and Grounds that torment Jirachi. With Earth Power, Magnezone, a Pokemon that could theoretically trap and kill Jirachi, is soundlessly covered as well. Celebi also covers Breloom and Landorus, both of which could be large threats to your team, and relieves pressure from Latias' shoulders to keep them down. Also, thanks to Natural Cure, you can switch into status and have it removed the moment you switch out. A summarized list of changes can be seen below.
Celebi @ Leftovers | Natural Cure
Modest | 56 HP / 252 SpA / 200 Spe | 0 Atk
Nasty Plot | Giga Drain | Earth Power | Psychic
Anyways, hope this helps. Good luck with your team, and Luvdisc'd!