Actually...he was. He did not expect any resistance to his spree and people would just flee from him in terror until he could come kill them. He was the "alpha predator" after all.
Ironbite-he also expected an army to spring up to help him and well...
If you look at the manifesto or plots or whatever of spree killers (the ones who actually plan their shit and talk about it, at least, like the Columbine kids), you'll notice that their plans are filled with what could charitably be called "delusions of grandeur." They expect to kill way more people than they end up killing and for their rampage to last for ages. They may even plan ahead with even grander schemes; Harris and Klebold alternated between fleeing to Mexico and hijacking an airliner to crash into a city.
One thing that still hasn't been totally figured out is why spree killers commit suicide so often. Theories include the killers being motivated by sudden shame or guilt after actually committing the act and self-punishing, as well as the theory that they feel such a sense of hopelessness at society or their lot in life that the spree killing is essentially a giant suicide attempt. The idea is that they already want to die, but are simultaneously fueled by hatred for the world around them. So it's a semi-literal killing two birds with one stone.
I think another theory, working along side the delusions of grandeur, is that some mass shooters possess a type of messiah complex like the Virginia Tech shooter. That guy felt he was, in a sense, saving the "innocent people" like himself from the supposed cruelty of the "rich and snobby" kids by making the "rich" kids suffer the same level of cruelty by shooting at them and killing and maiming them both emotionally and physically. He had already figured that he would get into a shootout with police, but regardless, he would die as a martyr for the cause of "inflicting punishment on rich kids picking on kids like him".
I think Roger was thinking along the same lines of a messiah complex. He had already stated in video and writing that he considered himself as a god of sorts, and the shooting should cement that into everyone else who "didn't get it" until the shooting. He probably hoped that with this shooting, he would die as a revered martyr to the "men's right to free sex" cause, and this shooting would cause conventionally attractive women to not say no to any mouth breathing creepazoid that wants her to be his "girlfriend".
