I apologize if I didn't mention enough how it could effect the NU tier. I realize that the thread isn't some random conversation where "hey! What if this guy had this! It'd be OU for sure!" I knew you were talking to me, I will give a more fleshed out analysis on how Roost on Mantine would effect the
NU metagame instead of the standard metagame in general. (i did have my reasons, but I was on my phone so I tried to make it short and sweet. Obviously, this wasn't as effective to the conversation as my tired mind had hoped it would be :P)
For starters, Mantine is already, in my opinion, an excellent mon in the NU metagame. It's amazing typing, unheard-of Special Bulk, good movepool, and handy resistances to Grass, Bug, Fire, Fighting, Steel (lol) and an immunity(ies) to Water (if you decide to use Water Absorb) and Ground make him a fantastic mixed wall with some investment in his much less remarkable physical defenses. He also carries a STAB in Air Slash that deals Super Effective damage to some of the most dangerous physical attackers in the tier (Primeape, Sawk, Scolipede) as well as many special attacking powerhouses (such as Ludicolo). His primary STAB, being Water-Type, is automatically good, hitting major mons like Golurk, Golem, and Charizard with great damage. His walling potential is also fantastic in this meta, stopping cold the previously mentioned Ludicolo, Gardevoir lacking Thunderbolt, any form of Gorebyss including after a Shell Smash, and most notably the recent drop-down Jynx, who has taken to most teams quite comforably as a late game cleaner, revenge killer, or setup sweeper. Mantine deals with her easily, as his most popular set, RestTalk+2 Attacks, allows him to absorb sleep and hopefully NOT draw a Scald and doing some decent damage with Air Slash (I personally run Toxic and Scald on the RestTalk set because I don't like how Air Slash only 4HKOs Jynx with no SpDef investment.). He has the capability to be the perfect Electric-Type lure in any situation, giving your Zebstrika a Lightningrod boost for example, allowing it to get a quick sweep going. He's truly an effective mon, shining most in the previous stages of the NU metagame for being able to wall Gorebyss (even after a Shell Smash!) and Ludicolo like it's not a big deal. What's bad for him now is that he has no reliable recovery outside of ChestoRest, which is fairly unpopular (I think I've seen 1, and the guy I played even said it sucked.), making him easy to wear down, even with neutral Special attacks.
Roost would remedy this. Roost let's Mantine heal himself reliably and quickly, without having to bet it all on whether or not he draws the right move. There are two big reasons I can think of as to why Roost would change Mantine, and the metagame around him.
- Mantine can now self recover. Honestly, this may sound like a "well no shit!" kind of thing, but people may not realize how valuable self recovery is for a wall. Mantine can actally stay around! Your team can no longer say, "Oh, I got this guy's Mantine under 60%, he's useless now!". Now, Mantine can roost up and be back on his feet (er, torso?) at the cost of a turn, removing the hard work of your opponent. It's Roost's main purpose and it lets Mantine perform its job multiple times in a match, as opposed to the single time or two he gets now.
- Mantine having Roost automatically frees up a single moveslot. This is amazing for the Manta Ray as it allows him to forego the usual Sleep Talk for a more useful coverage move, such as Ice Beam or a Hidden Power (HP Fire to troll Jynx maybe?). Personally, I could see a utility move being run over it, such as Toxic, Haze, or Mirror Coat. This allows Mantine to fully assume a role as a support Pokemon, and giving your team a way to keep set-up sweepers at bay or to cripple a foe for the rest of the match. People may not be able to use Seismitoad to counter their Mantine when they suddenly get hit with fully invested HP Grass. (of course that would be referring to part of the more common MANtine set, which would now afford to stay around longer with the addition of Roost)
I think, as a result of Mantine getting Roost, that Psychic-Type Special Attackers (Jynx in particular) may start running Psyshock more over Psychic, allowing the opponent to become more suceptible to being forced out by Physical walls, especially when choiced. It changes the game for many Special attackers, and most likely will force Ludicolo to drop even further in usage that it used to. All in all, it is a welcomed change, and I think it would change the meta.
So, sorry for my first post being so blunt (not only that, but talking about something going up in the tiers instead of how it may effect this one), and I hope you guys took the time to read it. I enjoy reading long, thought out posts, so I'm not sure why I'm not also doing them, but shoving a paragraph or two into the quick reply box and releasing it XD.