coffee grounds for fertilizer

A friend of mine has had great luck putting coffee grounds at the base of a rose bush. It is blooming like crazy. It is a Knock Out rose so I know they are generally easy to please. Are coffee grounds an OK alternative to rose food that includes preventative for black-spot and mildew? My tea roses are struggling (probably due to increases shade from a white pine) and I want to do anything I can to help them. I have so little sun that moving the bushes is not an alternative. Thanks for your help!