Using a flagship set of high resolution cosmological simulations, called Romulus, I predict the rate, properties, and host halos of supermassive black hole (SMBH) mergers and the dual AGN that precede them. Romulus includes a novel approach to SMBH sub-grid physics: Forming SMBHs from pristine high redshift gas, physically motivated tracking of SMBH orbits to sub-kpc accuracy, and including the effect of angular momentum support on SMBH accretion (Tremmel+ 2015, 2016). SMBH dynamics and accretion naturally respond to the changing structure of galaxies during merger events. Utilizing this advantage, I present a self-consistent prediction for SMBH mergers and their host galaxies. Following the growth history of merging SMBHs, I find that a significant fraction of SMBH mergers