But you're saying that Krookodile would be good for using Foul Play because of its attack stat
when Mega-Roserade said that Krookodile's attack stat doesn't matter because it doesn't use its attack stat, only the opponent's. The only consideration Foul Play has from the user is if the user is burned. The rest of Foul Play uses the TARGET'S attack stat.
If Pokemon A had 500 Attack, Pokemon B had 100 Attack, they both used Foul Play on Pokemon C, and both Pokemon A and B had no burned status, then they'd both have the same damage rolls on Pokemon C.