Coach John Dungworth felt all five players made a good contribution and told the club's official website: "They've all done very well so I suppose the follow-up from this is to either get them in to train alongside the existing professionals, or keep them under observation in their own environment."
Ramsey-Dickson, 23, had a spell at Chesterfield's League Two neighbours Burton last season but did not make a first-team appearance for the Brewers.
Former Wolves trainee Keane was recently captain of the development squad at Stoke.
Sammons, 21, came through the youth set-up at Birmingham and has played for Hereford and Worcester City since leaving St Andrews.
American Yao, 22, had a spell at Ipswich under Roy Keane in 2010.
Winger Bryan, who turned 23 this month, is currently at non-league Corby Town. He used to be at Watford and the Hornets loaned him out to Bradford last season.
- Sports & Recreation