There are 2 types of roll-form frame -- Box Frame and Lip Frame as pictured on our screen frame pages.
Roll-form screen frame is lightweight and economical, but weaker than extruded frame. It is made by taking a thin flat piece of aluminum stock, rolling it into a box shape and crimping the edge to keep the box shape.
Rolled aluminum screen frame is great for use in smaller window openings. Screens made of rolled aluminum screen frame are used by builders in most residential applications, and are popular for DIY projects because of the lower cost.