He won his first and only Ireland cap to date in June 2005 on the tour to Japan and was until recently a member of the IRFU PricewaterhouseCoopers High Performance Select Group.
The former RBAI pupil was also part of the Ireland 'A' squad that participated in the Churchill Cup in the USA and Canada in June 2006 and in England in June 2007.
Commenting on the move, Wilson said: "Northampton are an ambitious club. They are on their way up and I want to be a part of that. The facilities are top class and there is a good structure to the club.
Jim (Mallinder) and Dorian (West) are top class coaches and everybody who I've spoken to have echoed those thoughts. I want to improve as a player and have always wanted to play in England.
"It is a physical league and the quality has risen dramatically. I hope I can fit in to how the game is played there. I've been at Ulster so long it will be different. But it's also a positive move for me," he added.
There was be a familiar face for Wilson at Franklin's Gardens in the form of ex-Ulster hooker Paul Shields, who has played twelve times for Northampton this season.
A brief statement from Ulster Rugby concluded by saying that "everyone at Ulster Rugby would like to wish Roger all the best for the future."