Rokosjøen is a lake in the municipalities of Løten and Elverum in Innlandet county, Norway.
Rokoberget church ruins (Rokoberget kirkeruin) stand on a ridge south of Rokosjøen. Rokoberget church was dedicated to Saint Michael and mentioned in a papal letter from 1254. It is believed that the church was not used after the Protestant Reformation. The ruin was excavated in 1906–1907. The ruin is fenced with an information board outside the fence.