Plasmid copy number and Rop protein
Since the pBR322 is derived from the pMB1 plasmid (which is closely related to the ColE1 plasmid, it does indeed contain the coding information for the rop gene. It's expression will limit the copy numbers from the plasmid, so if you are looking for high copy numbers, the usage of a plasmid without the rop gene should be preferred. 

If it is only for the yield in a plasmid preparation, you could also simply scale up your production and make a midi prep instead of a mini or a maxi instead of a midi. It also depends, what you are planning with the plasmid. For cloning purposes mini preps with pBR322 have always given enough yield for me.