I have 6 IV Ditto and I am currently trying to breed for an at least 5 IV Roserade but, I'm only getting three and twos, I breed with my Inkay and Mantine and I got five even six IVs, am I doing something wrong? P.S I DO HAVE DESTINY KNOT ON MY DITTO, AND AN EVERSTONE ON MY ROSERADE
Give a Destiny Knot to your Ditto, and breed it with one of the babies.
EDIT: whoops didn't read that you're already using a Destiny Knot, but yeah, breed the Ditto with one of the babies as they'll have better IVs than the Roserade.