Both Roark and Cameron are visionary architects whose style is new and different. Society always regards anything new or different with wariness and suspicion; typically, society is made up of conforming masses who are deadened to their instinct that might alert them to the presence of genius, even if it is a bit different. People don't want to stand out, because it invites ridicule and judgment. Conforming is safer, and this applies to businesses as well as people. If a business is too bizarre, or a building too strange, most likely it will only appeal to a small few, which will hurt profits and success.
Unfortunately for Cameron and Roark, their work doesn't fit into stereotypical architectural standards that have been well-established in their society. Businesses want to play it safe, and cater to the masses, not to the few who would actually recognize their work for its simple, genius beauty. Cameron, who got a few lucrative jobs and a bit of noteriety and fame in his youth, did not "catch on" with the popular, conforming masses. So, it was hard for him to get work. On top of this, he refused to cater to the visions of others; this made him difficult to work with, and word spread of his cantankerous and uncompromising nature. People didn't even approach him for work, because he had a reputation for being stubbornly set in his own designs and ways. If they couldn't have things their way, they didn't want to work for him. Because Cameron--and later, Roark--didn't compromise his standards or lower them, he found himself struggling. It is an unfortunate result of the society; we see it today also. Often, genius isn't recognized until after it has left the world. I hope that those thoughts helped; good luck!