I would like to know whats ROAM and if it is really powerful, and where i will use it in. thank U PROgrammer

ROAM is a algorithm for real time level of detail terrain rendering. I think you might be able to use it for other models, but it would just really mess up the things.
Its best for terrain, and is the most popular method right now. It works by splitting and merging triangles to give more or less detail to the terrain...
look in gamedev.net''s developer resources for stuff on ROAM...
the other alternative is quadtrees