I've done every achievement except the ones that require the rose of oblivion. The ender dragon has been killed 5 times on the server, once by me. No roses generated.

What version of the mod are you on? There was a bug fix recently that allowed them to spawn again, so that might already be the fix you're looking for.

35.4 ty for already fixing it.

This issue was fixed in 35.5 so you'll just have to update!