There are accordion blinds that go both ways and can open top or bottom. They cost more than rollers.
But that’s not your question. And you already ordered rollers.

Roller blinds stay in place with gravity. The rolling action works mechanically in any direction.

But how to keep it in place upside-down? If you can put holes in place, parallel hooks/nails/screws at the levels you want should work. The key being the dowel rod that runs through the shade would have to be wider than the screen.

And the description doesn’t necessarily make it clear if this is an outside or inside hang, as methods will differ. Places that sell them generally have a blindcutter that can be set for outside or inside and also trim the rod. Generally there isn’t a charge for this when purchasing, might have luck taking them to a store if they need a trim and getting a complimentary cut if they are too wide. Leave the dowel longer.

Another one I’ve seen is getting a decent suction cup hook and putting a bit of looped paradors or something on to put on the hook.