A systemic pesticide applied to the leaves will slowly, but eventually, get rid of root aphids... good for bonsai Junipers but not really a usable solution for cannabis. Have to agree with Johnthemick, if clones came in with root aphids, they'd go straight in the bin.

The quickest way to check for root aphids is slip off the pot. Root aphids will leave a whitish fuzz that looks like beneficial fungi (mycorrhizal). The difference is that mycorrhizal fungi don't move and aphids do.

If you regularly need to buy in clones I think it would pay to have a small quarantine area, where new material can be pretreated before entering your garden space proper.