U can use textures if you export them . Right click, export as. And you can export Static Mesh by converting them to brush. Right click, convert to, brush. Then suppress the static mesh just let the brush. Left click on it. And in then files (extrem left in the tool), export as .t3d. And then import the .t3d files in RC. I try once and i don't remember but there was a failure with the uv's of the textures so it has not work like I expected.
Conclusion: Unreal Editor (Rc version) sucks and you can't import anything except .psk with no animations and you can't even add animations to them or it will fail (like if you try to put Battledroid anims to Grievous for exemple)
The only thing you can do is to import .psk from other Unreal Engine Game like I did for my mod. For exemple, Bulletstorm, Borderlands, Turok, etc... It's the only thing you can do and when you imported a .psk in Unreal Editor you can convert it as static mesh
It's the only thing you can do I think.
Sorry for this long thing but it's 3:27 am in France and i'm really tired right now x)