Very well, actually. But Romeo is the only person on stage who knows that Romeo and Juliet are now married - and Romeo is very aware that their marriage has been undertaken by Friar Laurence with the single aim of uniting the two houses, Capulet and Montague.
Tybalt enters looking for Romeo, determined to be revenged on him for his appearance (Romeo's appearance, that is) at the Capulet party the night before. Tybalt's words to Romeo, when he eventually turns up, are harsh and blunt and to the point:
Romeo, the love I bear thee can afford
No better term than this: thou art a villain.
Tybalt, the reason that I have to love thee
Doth much excuse the appertaining rage
To such a greeting. Villain am I none.
Therefore farewell. I see thou knowest me not.
Romeo refuses to rise to the bait: and is insistent on keeping the peace. When further challenged, he even goes further toward familial politeness:
I do protest I never injur'd thee,
But love thee better than thou canst devise
Till thou shalt know the reason of my love;
And so good Capulet, which name I tender
As dearly as mine own, be satisfied.
Romeo baffles his friends and Tybalt - why is he being so nice? Mercutio then challenges Tybalt and in the ensuing brawl is killed. He never knows about Romeo's marriage to Juliet.
Hope it helps!