Some 62 percent of Americans surveyed favor a proposal to protect all roadless areas of at least 1,000 acres in national forests, according to a poll released earlier this week by the Heritage Forests Campaign, National Audubon Society, and Wilderness Society. More than 70 percent favored a ban on oil drilling, logging, and mining in such roadless areas. Meanwhile, rumor is that an environmental impact statement may be in the offing as the Clinton administration moves to establish a permanent policy on road building in national forests. Previously, the administration seemed likely to settle for a more cursory environmental assessment, but greens are hopeful that a full-scale EIS will occur, bolstering their case that Northwest forests and the Tongass in southeast Alaska ought to be covered under a ban on road building.