I don't think its marked at the A630/A629 roundabout. But when you get onto what was the B6089 from there it is. Only noticed it this weekend when I took the little'un out.
Yes was in Rotherham at lunchtime today and it's definitely not been signed from College Road/B&Q r'bout (A629/A630) as yet. My tolerance of Rotherham Town Centre had already lapsed at this point so couldn't be bothered to trek up to Parkgate. As I'm sure you'll have already seen, the current OS mapping on Multimap has been updated.
Perhaps they are trying to spread this traffic around by sending through traffic on this new alignment of the A6123 from the College Road Roundabout to the Parkgate Roundabout.
Seems very plausible to use this as the signed route to Rawmarsh/Wath from the M1/Meadowhall to relieve the A633 in the vicinity of Parkgate Retail World. However, most locals more than likely already know the back roads through Greasbrough.