Read past that one, please.
I was only referring to combat encounters.
As for invisible creatures or not present creatures, no you won't reveal a thing in either vtt ( hidden feature) or during an encounter ( roll it before or roll different dice regardless the number of enemies, so players won't know the exact number).
Leaving apart the fact it doesn't matter when it comes to attack rolls and saves.
There you won't be able to cheat, while with a DM screen you easily could.
I am not saying it's the right thing to do, but pointing out that's the only way if you want to prevent cheating ( though you might not cheat even with a smile screen, players won't be sure of it). Leaving apart that, until now, there hasn't been a single point in favor to use a DM screen when it comes to fairness ( combat encounter, beware).