I think Rufus is lovely but not a fan of Rowan, in part because it’s quite often used as a female name and I think people might assume he was a girl if they hadn’t met him.
I don’t have a problem with the two Rs..name tapes will be easier...
Robert
Rollo
Ralph/Rafe
Reginald
Rory/Ruaridh
Roderick
Roddy
Richard
If you want the Norman name theme from Rufus, then Rollo, William, Geoffrey, Jocelyn, Hugo, Stephen all good Norman names.
If you want the Latin connection, Miles, Milo, Julius/Julian, Adrian/Hadrian, Augustus/Augustine,
Other Classical unusual names
Hector
Alexander
Ambrose
Alban