Otsemobor will join the Canaries on a free transfer when his present contract Gresty Road expires on 1 July.
24-year old Otsemobor started his career with Liverpool and had loan spells at Hull City, Bolton Wanderers and Crewe before he joined Rotherham United back in the summer of 2005.
Dario Gradi signed Otsemobor back in Janauary 2006 after he struggled to make an impact at Millmoor.
Semi was offered a new improved contract but rejected it and was placed on the transfer list, besides that Otsemobor made the League One team for the season.