Samurott - Use him for your HMs, he has good stats so if you considering HMs to be weak attacks, he will definitely be able to handle them well.
Crobat - Has useful poison moves and is of course a flying type. Since flying types have several advantages against Bug, Fight... they can definitely be used well.
Magnezone - Strong Pokémon, he and Electivired are for me the strongest non-legendary Electric types.
Camerupt - Earth and Fire? Think about the type advantages mate!
Roserade - Grass and status effects right?
Umbreon - If you hate the overpowered Psychic type and are scared of Ghost Pokémon, use Umbreon!
I don't have a clear view about their movesets, that is something you will have to find out. Learn Crobat Toxic and make sure Roserade can paralyze your opponents. This team could be very useful. You will have to do some research on how you can obtain them, they are all obtainable. Magneton evolves by leveling in chargestone cave, Golbat by friendship and Umbreon is a bit of a guess.