Building a roof over terrace
Your roof system is not appropriate for several reasons: 1) required slope, 2) structurally inadequate

The IRC Building Code requires a minimum slope of 2.5:12 for tile roofs. Your roof appears to be about 1:12. The tiles will need to be installed in what is called a “low slope application”, which includes plywood with a double layer of underlayment, which adds to the weight.

The loading your roof must support is tiles = 6 to 10 lbs. per square foot (psf) depending on the tile + 2 layers underlayment = 1 psf + plywood = 1 1/2 to 2 1/2 psf depending on the thickness + joists = 1 1/2 to 2 psf + drywall on ceiling = 2 1/2 psf for a total dead load of 11 1/2 psf to 15 psf PLUS a live load of 20 psf to 30 psf for a total load of 31 1/2 psf to 45 psf. That is extremely high for a roof.


The current structure could only support a total load of about 5 psf based on my experience. (I don’t have calculations to prove my statement.)
In addition, the structure must support a wind load and an uplift force, which depending where you are , that structure is not adequate.
Get a Building Permit and the inspector will reject it for you.