Will conifers ruin my new rose bed?

My next door neighbor has filled his garden with leylandii trees, which are at least 8ft in height. We both have medium size gardens. He has made a sort of maze out of them, so he has loads in a very confined space just the other side of my fence. Issue is, is that the only place I can put in a rose bed is against my side of the fence, meaning the roses will be less than 10ft away from all of his leylandii tress; as this spot gets the most sun.  The soil type is heavy clay, but the garden already feels hard underfoot despite the unusually wet spring we have had... so usually, I would need to apply a really good drainage system, but considering his roots have probably sucked all the gardens dry for at least another 2 houses down, should I even bother? PLEASE HELP