Required for seed coat mucilage deposition. Interacts with EXO70A1 and EXO70C1. Mainly expressed in cells expanding in a polar manner such as pollen and root hairs. Reduced pectin deposition leading to reduced seed coat mucilage thickness (PubMed:20618910). Characteristic pattern of pectin deposition to the corners of seed coat volcano cells (PubMed:20618910). 'Roh' means corner in Czech.