The neckbeards have 50 1oz hollowpoint slugs and 50 rounds of ten pellet 0000 buckshot.
The romans are armed with body armor, shields and short swords along with some spears.
The neckbeards have a 7x7 meter 3 story bamboo castle in the middle of a Wal-Mart parking lot that the Romans are trying to take by force.
The body armor would be useless against the slugs. The concussive force of the slugs would be enought to kill through kinetic energy alone. But if the Roman's could get them to miss enough of the shots the 00 would be stopped by the vest and shild combo easily. So I'd give it to the romans.
10 vs 100 and you may have fight but even then the parking lot is too far to run across. The castle is is just giving the handicap to the wrong side.
Romans, we're talking about career soldiers. First they would strategize and decide on tactics and probably flank the castle chopping down supports while using the spears as cover. Also is it likely they try to burn the castle.
the romans would simply hijack a passing home depot truck for the raw lumber and construct a ballista in place to take out the castle without suffering a single loss