Some of those roots are probably looking for something to twine into, they normally hang onto crevices in rock and wrap around branches. They will also root sections from the roots. My cats are always breaking off pieces of my dragon fruit and they all root, usually where they fall. On mine, they don't fruit until they have reached the top of whatever they are on and then arch over and down again. I think that is why commercially they grow them on a short post so that they will reach the top quickly and then start fruiting.
