Both former Iron players will spend the next three months at the Red Devils.
Ajose had a disappointing loan spell at Glanford Park last season, making nine appearances before returning to parent club Peterborough.
He was transfer-listed at Posh, and has spent the pre-season on trial at various clubs in a bid to secure first-team football away from London Road.
Forte had a much longer spell in claret and blue, making 119 first-team appearances and scoring 11 goals.
He left in January 2011 to rejoin former Iron boss Nigel Adkins at Southampton, but found himself dropping out of their first-team picture as the Saints surged from League One to the Premier League.
After three spells at Notts County and a month at Preston, this is his fifth time out on loan from St Mary's.