Do these bolt directly to my roof rails or do I need an adapter?

They mount at factory roof rail attachment points — no adapters required. You're bolting to hardware that's already there.

What fasteners do I need to install these?

The mounting hardware is not included in this assembly. Refer to your vehicle's service manual for the correct bolt size and torque specs for your roof rail system.

Is the matte finish sealed or will it need maintenance?

Matte finishes benefit from occasional cleaning but don't require special sealant. Wash like the rest of your paint — standard car care keeps it looking right.