just found this Roraima pic, here is the starting point. its a 6 day round trip.
we only set out with what turned out to be 5 days worth of food, so when we returned to the village we ate like ravenous buzzards. and we couldn't walk right for a few days.
humping 50 lbs of shit thru 3 rivers along the way and on and off rain was the most grueling experience of my life. absolutely worth it and i'd never do it again.
you have to have a guide legally to go up there, most people get a guide and a few porters to hump their stuff for them, but we opted to pay one porter as a guide, which was cheaper but more painful in the long run.
of course they also have helipcopter trips to the top, but thats no fun!