I'm not familiar with rose combs, but most EE's have pea combs. The combs on my EEs were still kind of flat at 7-8 weeks - yours may still be waiting to pop up too.
These are pullets, but at 6 weeks roos don't always have a very mature comb either.
These are pullets, but at 6 weeks roos don't always have a very mature comb either.

