I've heard of growing mint near roses to repel aphids, but this is a new one for me. I might try the mint tea and see if it works. Alternately, try a water soluble mint (mint oil like pure peppermint or spearmint won't dissolve in water without help--mint flavoring has been modified by mixing, usually with an alcohol or other chemical to make it miscible in water). Some essential oils are available that have been modified to be water-soluble. Flavor oils, like McCormick mint, should already be water-soluble, but check me. I use them and don't have an issue with them, but mostly use LorAnn flavorings instead.

Personally, I have my doubts on mint dissolved that much, and bringing it up enough in terms of strength is also going to cost a fortune--and dissipate fast. Mints aren't durable notes in any scent and the soaps I make with them tend to dull down fast on the surface (they reactivate when in the shower because one uses the top layer, exposing more mint to enter the air, and so on).

Mint oils actually have some warnings, so mind exposure to them. Peppermint, at full strength, will be extremely irritating on exposed skin. "Tingle" level is about 1%. I can't find a kill level for aphids.

I'd have to remain skeptical on the viability of mint compost to deter insect pests. WA state is the leading producer of mint and mint oil and while mint compost - a byproduct of the mint oil distillation process - is becoming very common here, it is just another form of compost with no special insect deterring characteristics that have been documented.

The compost is what's left after the process of distillation to remove the essential oils. With no essential oils left in the product, what exactly is providing the deterrence? btw, actively growing mint plants can be and often are prone to infestation by aphids, spider mites, flea beetles and cabbage loopers. If they bother growing mint plants with all their essential oils intact, why would applying mint compost or treating with mint oil provide different results?