It's extremely easy to have them both play together.
Just have Rodri do the Stones role, defend as a CB, then move into the CDM spot next to Zubimendi.
Rodri is clearly tall enough to win aerial as a CB.
I do want Gvardiol learning that role over Stones in the future though, he can be so good if you let attack more, which our CDM's would have alot more license to go forward than a left back.
Rodri contributed over 20 goals/assists last season. His talents would be wasted at CB. He can play box to box or in a double pivot with a license to press higher up the pitch and attack the box.