This appears to be the only known example of Roma wearing a decorated helmet for the entire series. The second coin below is a normal helmet.
VRBS ROMA
A.D. 332- 333
17mm 2.5g
VRBS-ROMA; Roma, helmeted, wearing imperial cloak; helmet decorated with a palm branch (or feather) and a volute on the bowl.
Rev.- She-wolf left with twins (Romulus and Remus); above, two stars.
In ex. TR•S
RIC VII Trier 542