Football manager Donald McDonald said the Roos would work hard to help the three players continue their AFL careers at rival clubs.
"We've spoken to a few of the boys at the end of the season and we'll get a few players a home during trade week, if we can," he told afl.com.au.
"But other than that, everyone is required."
Power, who played 84 matches with the Western Bulldogs from 2002-07 and is the younger brother of triple Brisbane Lions premiership player Luke, has added 39 appearances with the Roos for a 123-game AFL tally.
He crossed to Arden St via the trade period at the end of the 2007 season.
Harris appears set to miss out on the 150-game milestone with the Roos by one match, after being taken in the 2000 NAB AFL Draft (No.14 overall) from the Bendigo Pioneers.
Riggio has played 10 matches over three seasons after being drafted from Peel Thunder at No.28 in the 2005 NAB AFL Draft.
McDonald said North list manager Cam Joyce and recruiting manager Bryce Lewis were well advanced in their search for top draft talent.
"We just want to do all of our due diligence and find the best kids we can," he said.
"As soon as we get through this week and next week, we've got a good six weeks prior to the draft, where we do an enormous amount of work in that period.
"It's all under control."
