There are two ways to make some good notification of roshan
1) make some app that hacks time from dota2 memory
2) use dota2 to chat current time
I choose second way. I really don't like hacks
Alt+click the clock in game!
Okay, so we can either hotkey it in console or autohotkey.cfg by inputing:
bind key "chatwheel_say 57"
Here you can find list of keys.
Or you can edit chatwheel to show current time
Rosh respawns after a random time between 8-11 minutes*
Aegis is removed after 5 minutes*
*At the time article updated (2015-09-11). Check dota2 wiki to make sure