Unusual 'balls' on a rose

This rose is coming up from the root stock, the original rose died of drought. The original was red and this one is pink, has smaller leaves, and is thornier. Today I saw these 'balls' on the ends of 3 branches. I have never seen such a thing before. What are they?

 

Rose galls.

 

Simply cut it off (If you don't want it).

 

I'd leave them personally -- visual curiousity, with little long-term damage to the plant. Makes the garden more biodiverse.

 

True. I suppose it is up to personal preference and aesthetic or ecological appeal! :) I Agree with you though.

 

Thank you for your responses.