"He wasn't offered a contract and I explained the reasons why," added Keegan.
Defender Ramage, 24, and midfielder Troisi, 19, are both products of the club's youth academy.
Troisi has failed to make an appearance for the Newcastle first team and has been let go as Keegan looks to improve his squad.
"James Troisi has gone to play for Australia in the Olympics but he has not been offered a contract," said Keegan.
Keegan is expected to have funds at his disposal during the summer and has already stated he is planning a number of signings as he attempts to get the club challenging for a European berth next season.
"If I can get three or four players in to add to what I have got here - and we have that bit of luck you need with no injuries to key players - then we might be able to win the second division of the Premier League," he said after the 2-0 loss to Chelsea on Monday.
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