Tony Mowbray's side looked bright in the first half and went ahead just before the break when Kalifa Cisse turned Lita's cross into his own net.
Lita doubled the visitors' lead against the club where he began his senior career before Barry Robson made it three with a superb solo effort 13 minutes from time.
It got worse for the Robins in the final minute when goalkeeper David James was shown a straight red card for hauling down substitute Cameron Park in the area.
With all their substitutes used, defender Liam Fontaine went in goal for the penalty, which Lita slotted away with aplomb.
Source: PA
Source: PA