I've currently moved my rolls to be visible to the players (except things like Steath and social skills), but used to gm roll. When I did and these effects existed, I'd announce the die roll number before modifications. I did this both IRL and online, and found both to be a pain in the ass. I quickly moved to just telling the players the result on their end and letting them decide if it's worth it.
When dealing with unknown DCs (and enemy AC), I give them a few seconds to decide if they want to modify before I announce success/failure. Once I make the announcement, the result is final.
When dealing with unknown DCs (and enemy AC), I give them a few seconds to decide if they want to modify before I announce success/failure. Once I make the announcement, the result is final.