I was wonder if the 2017 Nissan Rogue has brake bad warnings. How do you tell if it's time to replace them?

The factory pads will have noisemakers on them (wear indicators) that will screech at about 2.5~3mm, but it's never healthy to let them go that far. There are cheap plastic gap gauges you can use for accuracy, but a good eyeball will usually suffice. You should draw the line around 3.5~4mm of pad left, and check the inside pads, those almost always wear faster than the outside set.

How loud is the screeching sound? I thought I heard a little screeching sound when I back out of the garage. But I don't hear anything when I brake going forward though. I am not good with cars, so I don't know how to inspect the brakes with my naked eyes. Do I have to jack up the car for that?

It will start small and intermittent, then gradually start screeching every time you tap the brakes. Pretty much all Nissans are infamous for squeaking a little on first use in the morning, especially in reverse. I don't think I'd be real concerned about that. If that's all it's doing, I'd say wait till your next oil change and inspect it while it's lifted. Checking the inners is hard-to-impossible without jacking the wheels.

There is not display reading that the pads are low.
There are "squealers" on the pads, but the best way
is to pull the wheels and look. Inner pads will almost
always wear a little more than the outer. So, if you
have about 1/8th" of pad left on the outside, then you
are less on the inside; change them. 3MM of pad is
when you should change them. The squealer should
be on the inside pad if possible, BOTH if supplied and
possible. A pad kit will have the new pad clips, springs
and squealers.

Pull your slide pins, clean, wire brush any scale, lubricate
and insert back into the bore. If they are real bad, just
buy replacement slide pins. Buy the copper paste anti-seize
for the slide pins. I use: