When exporting a Revit model of a sloped roof with IFC4 Reference view (Architecture) -preset, the exported roof layers have wrong model thickness in the resulting IFC-model. Seems like the exporter uses the thickness in vertical direction, while the expected behavior for thickness is perpendicular to the roof slope.
I'm using latest version of Revit 2025.3, a test project from empty template is attached.
IFC in Solibri
Roof in Revit