A common rust fungus of Rosa species. Common throughout Britain but not too many records for the Outer Hebrides – probably overlooked as there is plenty of Rosa rugosa about. The teliospores (resting spores) occur in the autumn.

References: 
Termorshuizen, A.J. & Swertz, C.A. (2011). Dutch Rust Fungi.
Wilson, M. & Henderson, D.M. (2011 reprint). British Rust Fungi.