Roof rack spreads the weight evenly on the roof edges, where the frame is thickest.
I'm thinking of putting a roof rack on my tercel, since i have one "lying" around. I have one on a KIA Sportage 1992 engine blown parts car. It comes standard on the old models. Problem is it CANNOT be unscrewed. Because the only the top part of the bolt can be reached so it just spins freely. So, im simply gonna SawZaw off the bolts and bolt it on tercel. {Cool part about it is you can move the bars down the tracks. Makes it able to transport most stuff.}
Even this roof rack says 150 LBS max. If that sounds good to you ask around Junk yards, i think u can get one cheap or something simular. On my fathers car, same roofrack was loaded up to 500 LBS and was still ok. Just higher Roll Over risk.

KIA Sportage 1992
I would worry more about your Shocks. I dont know how much weight they can support, they will certainly lower ur car down, might be permanently.