I'd say that depends on the plot. There's all sorts of sub-categories to romance where violence fits in just fine. Mystery-romance, suspension-romance, thriller-romance, and the list goes on...
As long as it doesn't come out of nowhere and shocks the reader without warning, there's very little you can't put in. But someone expecting a cozy and sweet love story, and who reads them because they enjoy a lack of violence, will probably not like your book if you surprise them with a fist fight or similar.
Me personally, I have no problem with it. Anger is a passion as well.
