The often-overlooked middle child of the Rotom family, Rotom-C is outclassed for the most part by Rotom-W in the OU metagame, as the latter sports both better STAB coverage and defensive typing. Rotom-C's dual STABs are resisted by both Grass- and Dragon-type Pokemon, which are very common. While it does have a resistance to the ever-present Water-type moves, it is weak to Ice attacks, common coverage moves for these Pokemon.
However, Rotom-C manages to create a niche for itself as an excellent member on VoltTurn teams thanks to its ability to defeat most VoltTurn counters. It separates itself from Rotom-W by being able to beat Gastrodon and opposing Rotom-W easily, as well as resisting Electric-type moves. Its dual STABs, while otherwise redundant, make sure Ground-type Pokemon that would normally switch in to block Volt Switch do not dare to do so in fear of a STAB Leaf Storm. Overall, Rotom-C is a very niche Pokemon, but it performs its role well. Do not expect it to easily fit onto a team, however.
This is the only set Rotom-C can run without being outclassed, utilizing its favorable typing, high defenses, and good resistances to common moves. It sets itself apart from other Rotom formes by being able to beat certain Pokemon that VoltTurn teams—and Rotom-W in particular—have problems with. Examples include Gastrodon, which would normally easily come in to block Volt Switch, as well as opposing Rotom-W. Rotom-C also has a resistance to Grass- and Electric-type moves, which Rotom-W lacks, allowing it to be a decent check to Breloom and Choiced Thundurus-T locked into an Electric-type move. While it is weak to Fire- and Ice-type moves, Rotom-C resists common Water-type attacks, such as Politoed's Hydro Pump, and can threaten there users with STAB Leaf Storm or gain momentum with Volt Switch.
Volt Switch is a great move for Rotom-C because it helps it support offensive teams by preserving momentum. You can opt to use Thunderbolt instead, as it helps Rotom-C better take on the likes of SubDD Gyarados. Leaf Storm still does a decent amount of damage to the ever-present Water- and Ground-type Pokemon in OU even without investment. Will-O-Wisp cripples physical attackers that would normally switch into Rotom-C, such as Ferrothorn and Dragonite. Pain Split is a mandatory move on this set because Rotom-C lacks reliable recovery outside of Leftovers, and Pain Split allows it to heal off counters such as Chansey and Blissey. It also works very well with Rotom-C's low HP.Team Options & Additional Comments >>>
If your team has a Celebi weakness, Rotom-C can use Signal Beam to quickly KO it. Rotom-C can run Rain Dance to back up Politoed's Drizzle. A Choice Scarf set is usable but is outclassed by Rotom-W. A dual screens set can be used with Light Clay, but there are generally better dual screens users, such as Espeon. Confuse Ray can provide confusion support, but confusion is generally not the most reliable status.
Checks and Counters
Rotom-C is walled by many Pokemon, such as Blissey, Chansey, and specially defensive Heatran. While it can run Trick to attempt to cripple these counters as well as other members of stall teams, the three will have a field day against Rotom-C that attempt to stay in and battle. Latios and Latias are also problematic as they resist both Rotom-C's STABs and can become deadly sweepers after just one turn of setup. They also have access to Roost, preventing them from being worn down by burn.
Grass-types, such as Ferrothorn, Virizion, and Celebi, give Rotom-C a lot of trouble due to resisting its STAB moves. While Rotom-C can run Hidden Power Fire, Ferrothorn can switch in on those that don't run it—or even those that do provided rain is up—and set up entry hazards. However, it is crippled by Will-O-Wisp and cannot recover with Leech Seed due to Rotom-C's Grass typing. Celebi is another great counter to Rotom-C because of its high Special Defense. It can take anything Rotom-C can throw at it and retaliate back by either gaining momentum via U-turn or attacking with Hidden Power Ice or STAB Psychic. Virizion is an unconventional yet effective answer as it can also use Rotom-C as setup bait due to its great typing, high Special Defense, and access to Calm Mind, Work Up, and Swords Dance.
Ice-types, particularly Kyurem, Kyurem-B, and Abomasnow, give Rotom-C trouble as they resist its STABs due to their Dragon or Grass typings; Abomasnow is able to revenge kill Rotom-C with Ice Shard as well. Numerous Fire-type Pokemon can also effectively check Rotom-C due to their resistance to Leaf Storm; these include Volcarona, Victini, and Ninetales. Ninetales and Volcarona both have naturally high base Special Defense, and the latter can set up on Rotom-C easily.
Last but not least, faster Pokemon that pack a strong super effective move can easily revenge kill Rotom-C; one such example is Mamoswine with STAB Icicle Crash.