Google has information on roof racks. Universals may fit your needs, but some aren't so 'universal'. The headliner may have to come down to drill mounting holes for the rails and some include a roof brace for added strength.
A clamshell is better at higher speed, quieter and fairly weatherproof. They should safely carry 150-200 lbs max.
Trunklid racks obscure rearward visibility. A trailer is another possibility.
Mopar roof racks are supplied mostly by Thule. These aren't really designed for cargo, but for watercraft, skis, bicycles, etc. Not any real weight carriers. What will you be carrying and how much weight?
Agree. Back when I was a youngin', My Dad bought a Sunfish sailboat that we carried on the roof of the Pontiac we had at the time. Then we got a trailer - much easier to load and unload.
A Class I (2,000 lbs) or II (3,500 lbs) should be more than sufficient. Try Draw-tite or U-Haul. You may want to have it installed professionally. For an '01 Intrepid the exhaust needs to be lowered temporarily for installation.