when to switch to scrying/sweeper besides on support
on support i know to get sweeper after i have sightstone but on the rest of the roles i just never know when to swap
3 Comments
For adc, switch to 
ASAP after level 9.
As jungler, anytime but keep buying wards before and after that sweeper.
Top can probably be fine with either trinket, but I don't know about mid (they seem to never buy wards...).
As a low ELO rubbish-y person I like to have the blue trinket on ADCs after level 9 if I have the spare gold (choosing between a BF and the trinket, take the BF sword, choosing between a longsword and the trinket take the trinket).
I like to get the Red sweeper after my core on any assassin to help with picks.
Obviously, supports pick Red up early. I haven't actually played jungle before... so I don't know. Top almost always stays with the upgraded yellow.
sweeper when you need to start clearing wards. or in other words when T1 mid turret falls because that is when people start to ward deeper into your jungle.