It seems that I can only roll from right shoulder to left hip. I can only speed vault with left hand for support and let my legs lean to the right. I can only tictac using right foot. The mirror situations are nearly impossible for me. Is this normal? Is it fine if I just keep it this way? Or is being "ambidextrous" really important?

I know what you mean, I vault with my left hand, my right is hard, but I am left footed (Right handed).

I would suggest practicing your other hand, starting just like you started with your left. Eventually, you will get the hang of it.

I think being ambidextrous in pretty much every facet is the best way, if you can roll both ways you won't have to force a roll no matter how you land, I've had plenty of times where'd I'd be coming in from a certain angle and if I were to force a right roll or something it wouldn't be fluid or just happen that well so you go with a left or vice versa. You want to be as versatile and adaptable as possible in Parkour.

For the Kong There are things like which foot you step into and out of the movement with, most people will have a preference, and like everything you should work being able to do it any way

Naturally you have a dominant side to your body that is more dexterous and a less dominant side that has more muscle but less control, being aware of this and trying to overcome its limitations is a worthy pursuit and will most definitely you will improve. But remember that unless it comes naturally to you being ambidextrous takes a lot work. I personally try to use my left hand ( the less dominant hand ) to draw and write with on my own, i also try to use my left hand for things i would normally use my right, like brushing my teeth. Also while standing lifting your knee and touching it with your opposite hand and then doing the same thing with the other leg as fast as you can, will help. If you do some of these things you will find that you are more comfortable doing other things with the opposite side as well, such as roles. You are teaching you brain to create cross connections between hemispheres to access information more speed and accuracy.

In another note the way to test which hand is dominant is easy its the one you write with.

To figure out what leg is dominant you have someone give you a slight push from behind and whatever leg you naturally use to stop yourself is you dominant leg.

To find out which Eye is dominant you look at something about 20 to 30 feet about that is about the size of your thumb, with both eyes still open you hold your thumb up so it obscures the thing you were looking at, then carefully close one eye and then the other, the eye still sees your thumb as over the thing you are looking at ( or at least close ) is your dominant eye.

To find out which side is your dominant side do a roll or just start spinning in a circle the side you spin and  roll to  is your dominant side.

also you have a dominant side and a non-dominant side, without being born ambidextrous, this will always be this case. you will always favor that side, which sucks if you hurt that side.

An interesting thing that i found was in my two step wall runs, if I pushed off with my left foot first, (Im right footed) then the right, i got much more height then doing it right, then left. While immediate grip on the first step is the same, the overall better technique of my right footed pass allowed for a much more powerful second step.

As far as vaults and whatnot, I try to alternate right and left.

It's really strange today.
I usually can only lean my legs to the right when I vault. So I practiced leaning to left for the past 3 days, now I'm much better at leaning to left and vaults that I can do leaning to right, I can't do them today.