Apparently the metal/gravel/concrete roofs can be used on a flat roof. I guess the fact that one of the roof types is made out of small loose stones should've made that obvious...but
The Sims 4 Building Roofs
Flat glass roofs? — The Sims Forums
Build help? How do I make this type of roof? — The Sims Forums
I took the advice to use platforms as my flat roof : r/Sims4
The Sims 4 Update: Glass Roofs & Gardening Changes - Sims Online
The Sims 4 Building Roofs
The Sims Resource - Flat Roof Trims
The Sims 4 Building Roofs
The Sims 4 Building Roofs
Ultimate Guide to Building Roofs in The Sims 4
Tutorial: Using Glass Roofs in The Sims 4 | SimsVIP
Tutorial: How to Build Roofs in Sims 4 | Learn to build great roofs in Sims 4!
Single Tile Glass Roof ?. — The Sims Forums
THE SIMS 4 Flat roof tutorial. - YouTube
The Sims 4 | GLASS ROOF HOUSE - SPEED BUILD - YouTube
Snow inside my Sims house because of the way I build it? - Answer HQ
Mod The Sims - Sims 4 Flat Roof
ROOF MANIPULATION, ROOF TRIM, & FLAT ROOFS // Building Tips & Tricks - YouTube
THE SIMS 4 Flat roof tutorial. | Shed roof design, Roof architecture, Modern roofing
The Sims 4 Building Roofs
Ultimate Guide to Building Roofs in The Sims 4
The Sims 4 Building Roofs
Mod The Sims - Modern Flat Roof
