The two will link up with the National League South side from this weekend when the Beavers host Dulwich Hamlet at The Beveree.
Both players have already spent time out on loan this campaign.
Kyei, who turned 21 this week, spent time at fellow National League South side Concord Rangers while Syla, 18, has made 20 appearances for Southern League Premier Division South side Kings Langley.
The two will be unable to play against Barnet the Middlesex Senior Cup Quarter Final.
We wish both Nana and Roy the best of luck in their time at Hampton & Richmond.