As Shakespeare has never indicated in this play the cause for the feud between the Capulets and the Montagues, these lines contribute to the senseless nature of the bitter quarrel. The phrases themselves make no sense in and of themselves, but neither does the feud between the two families.
Pointing to the use of the language of courtly love by Romeo in lines 185-195 is certainly important as you can contrast that with Romeo's lament about his lost love which is not phrased in this typical language. Instead, the use of oxymoron is prevalent. This employment of such a literary device conveys well the confused state in which Romeo is at this point.
There is, indeed, dramatic irony in Romeo's use of these oxymorons as later he will love his enemy--"O brawling love, O loving hate--when he meets Juliet Capulet.
This is a very important scene for describing one of the key tensions in the play that occurs again and again: that of hate and love, and how the two are related. Note the way in which Romeo, in his famous speech, relates the feud that we have just seen evidence of between the Montagues and the Capulets to his own feelings of love for Rosaline:
Here's much to do with hate, but more with love.
Why then, O brawling love, O loving hate,
O anything, of nothing first created!
O heavy lightness, serious vanity,
Misshapen chaos of well-seeming forms,
Feather of lead, bright smoke, cold fire, sick health,
Still-walking sleep, that is not what it is!
This love feel I, that feel no love in this.
Note the way in which all of these are actually contradictions, things that are really the opposite of the way they are described. This relates of course to the oppression that Romeo feels in his love-sick state thanks to his infatuation with Rosaline, but it also relates to the love that drives the Capulets and the Montagues to feud with one another. The love of violence and the hatred between the two families oppresses them just as much as Romeo's love for Rosaline oppresses him.