Well since Mathew is Hebrew for Mattathia, there will obviously be no Latin variant. Some suggestions though; Malleolus, which means hammer in Latin, Merula means blackbird, Metellus, which means army follower and Mergus meaning seagull. Other Latin names that really have no meaning but start with M; Messala, Maro, Marcellus, Mamercus...Unfortunately, the Greeks had way cooler names.
Except Rome spanned over hundreds of miles, and there were cases of Bastardizations of Latin/ local names in Roman provinces...you could probably find documentation of a name similar to Mathew. It wouldn't be purely Roman but it'd still have existed in rome