Pyramidal roof

[Keet]

Always download multiple formats (i.e. DAE, FBX, OBJ/MTL). Sweet Home 3D can import DAE and OBJ/MTL directly. One may work better than the other.
FBX you can import into Blender and export as OBJ/MTL. In some cases this gave me a better result than using the downloaded OBJ/MTL.

But... it's such a simple roof, why don't you create it yourself? The roof generator can create the basic shape and you can add textured cylinders for the corners. I think that's not done very well on the model and you can do a better job yourself.
Since you have bought the model you have the texture too so you can use that for your roof.
Nowadays I don't download anymore, I create everything (except characters) myself.