The Brew Cabin

Only when I have no money - now - am I a DIY enthusiast. So I hope someone can advise a rank amateur.
I have a garage - floor, walls and flat roof all in concrete. The roof has been covered in 'Isoflex' a rubberoid product from Ronseal. There are small cracks in the roof so I assume this was done to keep out the rain.
Bizarre as it may seem, the layout of the house - split level - means that it it easy to walk from the kitchen straight onto this garage roof and overlook the garden. BUT the Isoflex will not stand up to regular walking on and certainly not a table and chairs. I emailed Isoflex/Ronseal and was advised there is no surface you can put onto it.
This may be true but would it be completely daft to place small discs (made of what?) say 2cm thick onto the isoflex so that these can support in each corner concrete paving slabs with say, 5mm gaps in between the slabs so that the rain can run between the slabs onto the isoflex and away? I gather that if you put slabs direct onto the isoflex they will lift.
Or has anyone any other suggestion?
Hep would be much appreciated.

You might think it's daft, but a company by the name of Caro make a nice living producing such 'little discs' that allow flags to be laid to flat roofs while allowing water to flow beneath!

The usual spec is to re-cover the roof with a particular membrane or tanking, then the Caro-Supports, and then the lightweight flags, which are sometimes known as Promenade Pavers (complicated, because Baggeridge Brick make a range of clay pavers sold under the name 'Promenade').

I've only ever been involved in this type of job once, and the roof had to be demonstrably strong enough to carry the weight of the paving plus the additional imposed loads. This 'proof' is done by a structural engineer - just laying flags to your flat roof quite probably invalidates your Bricks'n'Mortar insurance!

I'm not sure how suitable a job it is for DIY. From what I recall, and I'm going back about 8 years or so, it was ridiculously expensive work. The membrane/tanking cost a small fortune, and it took us twice a slong as anticipated, but, to date, there's been no comebacks (Thank God!!)