Block Suggestions

I have built a mine entrance/forge room and now it needs a roof. For this type of structure I don't want anything that looks like an expensive material, yet it should appear to be functional and able to keep the rain out. The roof will be built in the standard a-frame structure with a combination of square and triangular blocks. I would love to hear any suggestions from this community. I'll be sure to show a picture of the structure right here in this thread after the roof is complete. Thanks!