You can use Pandora.com and just type in "rock music". NPR.org is not a radio station but a website. However they have a music section with radio streams available and music tap where you can find a rock genre to search for good bands. You should also browse their "tiny desk concerts" section, it has great videos!

Marco, I enjoy "Adult Alternative" station. I tune in on "Tune in" app. It's a cool radio. It's song by 24 hours per day. I hope you enjoy it.

"I am also interested..." :P