Sulis isn't neither Roman nor Greek, she is the Celtic goddess associated with the springs at Bath. When the Romans came to Britain they learned about Sulis and felt that her attributes were similar to those of Minerva, the Roman goddess of wisdom. In typical Roman fashion they linked the two as if they were one goddess, when in fact they were nothing of the sort.
Very little is known about Sulis since the Celts left no written records. All we have about her are some inscriptions and an image found in connection with the springs in Bath.