in a similar boat is
google.... Fluid Applied Rubberized Asphalt
American Hydrotech is generally considered design basis in USA market.
The roofing materials are heated and mixed in a hopper to temp and sprayed to the substrate. A good PRM roof on a concrete substrate will last until we're both dead.
there is a lot of information about the design of the existing roof (especially the substrate), condition of the existing roof and structure, cost, availability of contractors skilled with this roof, desired (or code required) total R-Value, location of dew point concerns, desired life-cycle, foot traffic, roof equipment...... that goes into selecting the most appropriate roof. It may be worth it to you to consult with a local Registered Roofing Consultant (RRC), a local engineering firm that specializes in envelope services, or a local architect to sort it out....
unless it is leaking... before you engage, i would start looking at the product lit from the manufacturers to get a familiarity with what's out there. If your roof works well within the manufacturer recommended details they publish, that is a good start. roofing manufacturers have tech sales reps that should be very knowledgeable although biased to their product.