If you want the decking surface to be level the sleepers will need to be tapered to compensate for the slope in the roof deck.
Roof deck sleepers.
For a large deck where flat sleepers are too thin to taper you can use 2x4s or 2x6s set on edge.
Sleepers need to be arranged to not block impede drainage flow.
Durable hardwood lumber sleepers work well too.
It s best to be able to clean it out often.
Construction sleepers must be 16 406 mm oc maximum spacing.
Sleepers come in a variety of materials but only wood sleepers are regularly used in deck building.
You could glue the strips tongue sleepers or just make them a bit wider and rely on pressure to keep them in place.
Concrete and metal sleepers work well for building retaining walls but these materials are too hard to attach normal deck boards to for a basic deck.
A properly constructed epdm roof should last 40 or more years.
Sleepers must be securely fastened to the subsurface per codes.
If pressure treated lumber is used for sleepers the grade and durability of the material should be considered prior to construction.
Treated and untreated wood sleepers come in a range of sizes because nearly any solid piece of lumber larger than 2 by 4 inches can be used in this way depending on the size of the deck.
I d put down strips of rubber roof under the sleepers.
Recycled plastic lumber is often used for sleepers because it is rot resistant and should last as long as the decking material and the rest of the deck structure.
Sleepers must made from be rot resistant materials.
O recommend using a 1 4 6 4 mm plastic spacer under the sleepers to aid drainage and keep them dry.
Rooftop decking attaches to treated wood sleepers separated from the roofing by strips of epdm.
It s a wash as the deck keeps the sun off the roof which is good but it also stores a lot of debris in under there.