Carpet as a weed mat

I have a friend with a huge weed problem with her roses. She sprays several times a year but the weeds keep coming back like jumping jacks. I was wondering if an old wool carpet laid on the ground with new soil and compost spread several inches thick over it might solve the problem once and for all? Someone suggested carpet is organic and the worms might like it – and it might be better than black polythene which can make the ground a tad smelly.