GAF has a TPO product that is Fleece-backed. It allows you to install this new roofing system over your existing Oklahoma roof. You can even install it over abrasive surfaces! If your current roof is a concrete or granule-surfaced membrane roof, no protective sheet is required to install this new roof.
Additional pluses: it can be mechanically attached, fully adhered using adhesives, or mopped in hot asphalt.
And, to meet the demands Oklahoma Commercial Roofs, it even has configurations for enhanced hail resistance!