Especially if the takeover of the Hijaz takes places before the division of the empire, then Islam is guaranteed to be butterflied away.
As for wether or not a Roman conquest of the Hijaz is possible; the answer is yes - if the Romans really wanted to conquer the Hijaz, then they could have done that.
However, why on Earth would the Romans want to conquer the Hijaz?
The area is sparsely populated, the local economy depends entirely on the trade routes between Yemen, Syria and Egypt, and due to the rough coastline, there are only a few small coastal villages.
The only thing in the Hijaz that the Romans would have considered interesting, are the gold mines not too far from Mecca and Medina.
And I'm not sure wether these mines were in use during Roman times.
Only if the Romans would have managed to conquer Yemen would they have had a good reason to control the Hijaz.