What time specifically will preseason be rolling out?

Riot doesn't usually provide an ETA for uptimes after patches, especially pre-season. These changes are going to be pretty hefty, so it's really hard to tell.

Basically think of it as this - they have a fire hose (the patch) and a large vat of water (all the preseason patch changes). Depending on if the hose kinks during the process, it could take more or less time than they plan - so they generally say "we estimate the battlegrounds will be unavailable for x hours" - but it could end up being more or less.

On the bright side, none of us have an excuse not to get a good night's sleep!

Well it will most likely happen between 2-4 am.

Soon TM