For us, it was not remotely close to being viable, off by 5-7x as I recall, and our roof had good orientation.
Whatever the barriers, roof top solar is not taking hold very quickly.
Oddly enough, back during the recession of 2007-09, there was a program derisively called "Cash for caulkers" after the poorly-executed "cash for clunkers" failed. It was a way to subsidize energy-efficient retrofits of existing houses.
While my political leanings make me bristle at it, from an economic standpoint it makes a lot of sense.
The biggest issue with energy-efficient retrofits is that the upfront cost is often quite high, but the savings are spread out over time. So you need money now in the assumption of long-term savings. It's the opposite of a get-rich-quick scheme! Further, I think a lot of energy efficiency upgrades are hard to recoup in the sale of a house, so unless you stay in the same house long-term, you'll never make your investment back.
That said, energy efficiency is a net gain to society. It reduces aggregate demand, reduces the environmental impact of generating energy, and in the long term reduces cost to everyone.
So it's the PERFECT sort of thing to subsidize, because it has a lot of positive externalities that are difficult for the purchaser to recoup, so energy efficiency upgrades receive under-investment in the market.
But that's why rooftop solar doesn't take off. If I have to pay $15,000 to put solar on my roof, but it will take me 10 years to recoup the investment, I have to KNOW I'm planning on staying in a house for 10+ years. That's hard to do in our modern world. Hence fewer people buy these systems than would do so if there was a better business model that reduced the upfront cost.