PVC, Rubber, Built Up, Tar/Bitumen, Metal, etc...Generally, you'd be looking at somewhere between $4-7/sf in much of the country (and I'd think western Washington should be in that group). 

@Michelle BrightThat "silver coating" is an aluminium pigmented asphalt which is rolled {painted} onto an modified bitumen roof.  

When you say flat roof, hopefully you have a slight slope, because there are "flat" roof systems using modified bitumen (peel and stick nowadays) or tpo.

@Matthew McCormick its a bitumen (asphalt rolls) roof, has some tear down and aluminum coating already per inspection report seems like seller did that to extend life of roof maybe 5 years ago. 

epdm webpage - https://www.firestonebpco.com/...Brochure - https://www.firestonebpco.com/...You could also have a Modified Bitumen roofing (aka rolled roof).  

@Waylon Zook Based on inspection, I currently have single ply modified bitumen.

Basically, they have more bitumen and probably thicker paper.  

My question is - Do I go for the EPDM rubber roof or the GAF self-adhesive Modified Bitumen roof option? 

My question is - Do I go for the EPDM rubber roof or the GAF self-adhesive Modified Bitumen roof option? 

Bitumen roofing is a good system (particularly mod bit roofs).