Cheltenham have signed Eliot Richards on an 18-month contract, along with fellow forwards Denny Johnstone and Wes Burns and midfielder Jordan Wynter.
Richards, 23, signed for Tranmere in the summer but was released by the League Two club on Monday.
Wynter, 21, has also signed an 18-month deal after leaving Bristol City, while Birmingham's Johnstone, 20, goes back out on loan after being recalled from a spell at Macclesfield.
Burns, 20, had been on loan at Oxford.
Johnstone and Burns have signed until the end of the season.
Robins boss Paul Buckle has also extended the loan deal of Liverpool defender Lloyd Jones until May.