This is personally my favorite song on keys in the entire Rock Band catalog. In addition to being an awesome song in general, it's also one of the most fun to play.
If you wish to play this song on pro keys, be ready for a challenge, even if you're an experienced player. If you're up to the task it can be one of the most rewarding experiences in the whole game.
For the most part, the keys part is entirely rhythm. There's no solos, and arguably the keyboards never really take the lead. However, they're still a huge part of this song, and there's still a ton of variety.
You'll mostly be playing along with the chords in an improvised blues-like manner, often throwing in some licks in between the vocal phrases. Get ready to jump around a lot, because the keys part doesn't like to sit still. Often you'll be playing the same chords in a wide variety of ways, and a wide variety of rhythms. Never does it get boring or repetitive.
If you're the kind of person who's looking for a challenging keys experience, this is the perfect song for you.