Yes, you can stream Ravens games. There are a few ways to do this, depending on your location and whether or not you have a cable subscription.
If you live in the Baltimore area, you can stream Ravens games on WBAL-TV's website. You'll need a cable login to access the streams, but it's free if you have one.
If you live outside of the Baltimore area, you can still stream Ravens games through NFL Game Pass. This service requires a paid subscription, but it will give you access to every NFL game, including the Ravens' games.
Finally, if you just want to catch occasional Ravens games and don't mind missing some of them, CBS All Access offers streaming of all NFL on CBS games. This service starts at $5/month and also includes a lot of other CBS content.