4th Gen Need one more pokemon for my team

So I'm at my wit's end here on which pokemon to fill my last slot with. I'll list of my team members but before I do that there are a few things I want to let you guys know.
1) I am using Pokemon Pearl
2) I don't like training Legendaris or Pseudos and I dont like training pokemon that level slowly
3) I realize that some of my team has "Undesirables" for a lot of people but I like these pokemon so I'm keeping them anyways.

Team:
Infernape
Kricketune
Pelipper
Gardevoir
Rotom

If you know how to get a shiny stone, Roserade could be a cool addition.