I don't usually DM but think it would be a good idea whenever something requires 10 or more dice, as acutally rolling that many slows the game down too much imo (and there's also a good chance the person rolling will lose count, make a math error, etc.) If the players want to roll for their own abilities and attacks (such as a wizard casting Meteor Swarm and rolling 24d6), that would be fine with me.
If I'd GM at a physical table more often, I'd ask the Meteor Swarm wizard to take the average of 22d6 and roll 2d6 afterwards. With that many dice you end up close to average anyway - usually. Well, I wouldn't mind him rolling 24 dice for fun one or two times, but on the long run I don't want that at a table.
Online it's not an issue for us - Roll20 has dice rolling integrated. You can even do some scripting to do an entire full-attack (including crit confirmations and damage) with a single command.
In the few cases I need a separate dice roller, I use the ancient WotC one: https://www.wizards.com/dnd/dice/dice.htm
As a GM, I only roll physical dice on a major occasion, in which case I do it out in the open. (EG: They've been planning a way to kill the BBEG for 3 books, finally get the chance and their plan depends on the BBEG failing at something. Rolling that in front of people is great fun.)
Otherwise, I use CombatManager as I am lazy and it does all of the math for me.
As for my players, they typically start to use a rolling program once they're around 8-10 dice. Sometimes earlier, but I leave that up to them.
I actually used it as a player in our last campaign. I had a Sanctified Slayer, and played him as an archer. Later in the campaign I was having to roll for 5 arrows hitting, and most of those arrows doing their regular damage, greater bane damage, holy damage, and sometimes sneak attack or critical hit damage. We were actually doing roll d20 at the time due to COVID, so I was putting formulas, but even in person I'd just use the dice roller from Google so it wouldn't take as much time.
J
We started using Roll20 because of Covid, and I have to admit sometimes it's been a real time-saver.
In one game I'm a Bloodrager (changing bonuses from Rage) with one level of Oracle (changing bonuses from spells). There's a wizard in the party (more bonuses) as well as a bard (all the bonuses). Having my attacks macro'd has really helped me keep on top of things.
We've been using FantasyGrounds since about the mid 2000s (if I remember correctly) because while my group all used to live together in NoVA, we're now scattered about and we've added additional players as well. COVID had literally zero impact on our games, except the guy in Texas was suddenly on time for games because he was already home instead of coming home from work. So we use the built in dice roller. But WAY back in the 2.0 days (mid to late 90s) I had a player who custom built some tools that were quite slick (for the time). I don't think I ever found anything I liked better than his custom stuff, although I always suspected he back-doored the tools so his rolls would be high and the ones he gave me (as DM) would roll low. ;-)