"My questions are what are the big benefits to having a roller cam?"

Independance from overpriced boutique high zinc motor oil, more hp and torque throughout the powerband, often noticeably better/stronger idle quality as well.

"Which is better: solid or hydraulic roller?"

Solid is the ultimate for performance use but there are many excellent running cars with hydraulics out there also.

"Do you have to adjust the valvetrain the same with a solid roller like you do a solid tappet?"

Yes you do.