Sell By Metre

We have a requirement in which we would want to sell a Product as a "Roll" (EA) as well as in "M". The product needs to be ordered in "Roll" always.

If we set up a single item with Standard UOM as "EA" and Selling UOM as "M", the issue is when a Roll is sold the quantity has to be in terms of "M"  and need to rely on the store associate entering the right quantity (M equivalent of the roll).

Would like to understand if there are any other possible solutions for such a set up.