Yep, just set them free

I usually tap them in another jar with some supplements in it,
shake them for a while and throw them in.
This makes them climb some less, until the powder is gone
Only make sure not to get to many of the supplement in the viv with the flies.

You also remove a great deal of mites this way,
before setting up a new fly culture throw them in a cheap supplement like gistocal and throw them in a fine mesh sifter to remove the powder and mites from the flies.
This will improve youre cultures rade of reproduction since mites can literally destroy your fly culture.
With this method, you immobilize the mites, that will lose their grip of the flies and the mites won't be booming on you're medium before you're flies do.

The leucomelas also love small things like springtails, small tropical woodlice, aphids,
flour beetle larvaes, milkweedbugs stage 3-4, wheat weevils, bean beatles and so on.
A wide variaty of foods is essential to them and makes the need for supplements minimal.