He was great in a lot of seventies moves, including one of my favorite all time films, The French Connection.
You have to see the Gene Hackman car chase.
http://www.youtube.com/watch?v=e2HBSuM_fLQ
The Seven-Ups is another classic seventies hard core cop movie that Roy Scheider stared in. Total Grindhouse kind of picture.
Check out the car chase on this one, Bill Hickman, the stunt driver from Bullitt, drove one of the cars.
http://www.youtube.com/watch?v=hg4QtYizPKM