Roughness 3D model seams in Substance Painter typically result from inconsistent UV island alignment or flawed texture baking.
UVs with gaps, overlaps, or uneven padding cause roughness value mismatches at edges; baking issues (e.g., wrong cage size, misaligned smoothing groups) also create seam inconsistencies.
To fix, ensure UVs have uniform padding/alignment, re-bake with a properly sized cage, or use Substance Painter’s "Seam Fixer" tool on the roughness map.