Whether or not Roost Mega Heracross would exist is irrelevant to this thread. Even if we assume that it did exist if Roost Heracross won, i wouldn't allow it to be discussed in this thread or to exist in the ladder because it would completely overshadow regular Heracross and would make the whole theorymon pointless. So, you can say that Roost Mega Heracross would exist, but it would have been banned in this thread and the ladder.Poison Heal Snorlax looks like it's winning by a landslide, and for good reason (add my vote to the masses!). Even without Facade, its viability skyrockets with great passive recovery (which, barring clerics on your side or perfect timing, is unaffected by Knock Off) and immunity from the burns it so hates. It would certainly play differently from Gliscor, but would also be a perfect partner to the scorp just like the Gligar/Snorlax UU combo I so loved in Gen V.
Snorlax walls special attacks, Gliscor walls physical (and absorbs Snorlax's only weakness, Fighting), both constantly recover, one can set up Rocks while the other Whirlwinds...so exciting. Sure it isn't perfect (Keldeo in particular laughs at this core) but combining Gliscor with the closest thing we'd have to an offensive Blissey would be a blast.
Facade is icing on the cake. The important thing is that Curselax can suddenly be a thing again.
(Also, sorry, but the whole "No MegaCross with Roost" is a bit too much of a stretch from the meta for my taste. Every change proffered to this thread are things that GF feasibly could've done given the current mechanics, and saying Roost somehow isn't allowed on MegaCross is a fundamental mechanical change that would set a terrible precedent for what so far has been a very interesting thread/meta. Thankfully even regular Hera with Roost is pretty boring, especially against the support behind Chandy and Lax in this round, but I really hope this is the last time a mon is considered that changes the actual mechanics of the game.)
Poison Heal Snorlax