Hi, if i was you i should learn texturing. But it also depending on which style you use. I am a low poly modeller, you should it let it rely on what style you model in. And yes you can import textures to roblox if you export it from blender as a .fbx file.
with the new pbr textures its not as important since its way easier to just apply them in studio
but if you want to start making renders, realistic models, or scenes in blender then you should learn to texture
wdym by this you dont need a separate file or anything its just the first time that you use a new texture it will upload it to your account as a decal to be put on the mesh
I never really export textures from blender so I wouldn’t really know. but if you upload the texture as a decal before you import the models I think it will automatically apply it