Not with the resources on Earth, but the ones in the belt yes..... If you stick enough rocky material together it will form into a sphere, and there is more than enough (but we would probably have to destroy ceres)

Oye Beltalowda sasa ke?

Does making a planet make any sense? No, with that kind of technology, it would be easier to just terraform Venus and Mars. Or mine the Jovian system and turn it into space stations.