It's so useful, it takes 10 seconds usually i've looked up their main roles and main champions before the banning phase is over, if you got 3 auto-filled with you it's most likely a loss.
Otherwise looking at your replays is something nice too, you'll see mistakes that you wouldn't have noticed before, even small things like "at this moment i was affraid of this champion but he already used his hook 5 seconds ago so i should have been able to poke" from that point you make a mental note to play around his cooldowns next time you're into this matchup.
Something i started to do recently is timing summoners spells, as soon as the pre game lobby is over and the game launches itself you have access to your enemies runes in details under the "live game" tab on your op.gg profile, something nice is to make a little note on a paper near your keyboard that looks like something like that :
https://i.imgur.com/ShdnXj2.png
( this one might be outdated i'm not sure if unsealed spellbook still gives cdr or not ), but you get the point, you need to have chat timestamps on in your settings and set up the binding to display all chat logs. when someone uses a summoner you ping it asap. then when you've backed and move back to lane you get time to press that binding, look at the timestamp and write things like "adc f 1542 top tp 1625". It's not that easy at first that's why you do that when coming back to lane, you'll only be able to track a few summoners but once you've done it for let's say a week you don't even have to look up your little paper note anymore you'll just know the cooldown by having looked at their runes once before the game starts and pressing tab. It's really useful to know when exactly someone will have his summoner spells up your whole team will benefit from that. It's like playing without the autofocus on your champion, it takes a week or two to get used to it but once that's done it'll make your life easier.
