Argthtjtr

The phrase "that's how we roll" (along with variants) seems to have become increasingly popular in recent years. It appears to draw attention to one's behavior or policies, asserting -- sometimes ironically -- the correctness or importance of them, as in "that's how we do things around here."

How old is this usage and where does it come from?

The OED says it's US slang originally in the language of rap and hip-hop. It's sense VII.36.f. (and sense VII.36.e. is "Let's roll"), under sense VII:

To move or convey on wheels or rollers, and related senses.

This is their first quotation of the phrase:

1991 ‘Hammer’ & F. Pilate (song title), This is the way we roll.

The video shows MC Hammer driving a car and some of the lyrics are:

Down the highway

I'm doing it all my way

Money in my pocket (Yo)

I'll say it feels good

That I got it like that

My top dropped

Her hand is in my lap (my lap)

Alpine kickin' another selection

The girlies keep lookin' in my direction

My tank is full

My fame is strong

I got it like that

So I'm rollin' on...

This is the way we roll

We roll...We roll

This is the way we roll...Rollin'

(Rollin'...Rollin'...I'm rollin' on)

This is the way we roll

We roll...We roll

This is the way we roll...Rollin'

(Rollin'...Rollin'

All through Oaktown I'm rollin' on)

The next quotation is from Puff Daddy's 1997 "Been around World" lyrics.

Searching Subzin.com, the phrase was used in many Hollywood films in the 2000s, but the earliest I found was from a song in 1999's Deuce Bigalow: Male Gigolo: Wyclef Jean's 1997 "We Trying to Stay Alive" (the first single from his debut solo album) and these lines delivered by his cousin Pras:

Well you can tell by the way I roll shorty

that I'm a ladies man, a business man

As an aside, the song samples the 1977 Bee Gees hit "Stayin' Alive" and, according to Rap Genius:

Pras' delivery of these lines is accompanied by a Bee Gees-esque falsetto, and the words and melody are a shout out to the opening of the original “Staying Alive”:

Well, you can tell by the way I use my walk

I’m a woman’s man, no time to talk

The earliest non-literal use of this phrase I find is in the 1995 song/album "How We Roll" by a Latin pop group called the Barrio Boyzz. The chorus runs:

This is how we roll

And we're rolling like that

So honey's come in

Kick off your shoes and lay back

(Champagne, caviar, and bubble bath)

This is how we do

And we do it like that so honey's come in

Kick off your shoes and lay back

(Champagne, caviar, and bubble bath)

Complete lyrics are here, and a video of the song is here. The sense here is clearly sexual.

EDIT:
Hugo's answer provides an earlier citation and a context for this. Clearly the Barrio Boyzz, a Latin pop group " crossover as mainstream American pop singers" (Wikipedia), adopted a phrase made popular by M. C. Hammer to an explicitly sexual context, cross-referencing a sense of roll which had been current for at least three generations.

The phrase subsequently shows up in many titles and lyrics from pop and hip-hop artists, and in a 2007 rap-style film score by Alvin and the Chipmunks. The sense is generally that you describe, and that given by contributors to Urban Dictionary s.v. "Roll":

Stating your philosophical stance on a situation with a affirmative predisposition.
That's how I roll.
i.e.-Jack black kicking Will Ferrel's dog over the bridge after Ferrel ruined Black's motorcycle, then stating to Ferrel, "thats how I roll".
you aint got my cash, I'll bust a cap in your ass. Yeah nigga, thats how I roll.

A word used to describe a particular person's behavior or idiosyncrasies.
I work hard and party hard. That's how I roll.

verb; to act like one normally does
You see these spinner hub caps? Yeah, well that's how I roll.

Googling around for the origin of the phrase, how I roll, I found a commenter who said they heard the character B.A. say it on an episode of the television series The A-Team, which ended in 1987.

http://www.606studios.com/bendisboard/showthread.php?74187-What-s-the-origin-of-quot-That-s-how-I-roll-quot

All above are incorrect. That's how I roll refers to a pool shark who makes a combination shot into the nine ball to win the game of nine ball. The expression has been around forever.

I'm an immigrant to the U.S.. But I believe that the phrase "That's how I roll" and "That's how we roll," refers to rolling a cigarette, more commonly, a marijuana cigarette.

The phrase implies that you're "cool" at the way you do things.