The 31 year-old utility player who has spent time with Bolton Wanderers, Port Vale, Carlisle and Darlington has impressed boss Andy Scott enough to take a longer look at him.
Smith signed for Belgian side Royal Olympic Club de Charleroi-Marchienne last year but is now a free agent and looking for a move back to English football.
The Millers leave for their pre-season training camp for a week after tonights game with Sheffield Wednesday at Don Valley.