I watch a lot of vintage movies and recently saw Mickey's first dramatic role, 1950's Quicksand. Shedding his wholesome Andy Hardy image, he played a garage mechanic who gets deeper into debt and trouble with the law. A pretty decent little B-style film noir and Rooney proved he was a good actor.
I've also seen a few of his 1930s-40s Andy Hardy movies that made him a star. Corny products of the time, but good harmless fun.