Debbie Roop's modest three-bedroom house in south Stafford County was assessed at $43,900 when she and her husband bought it in 1981. A few weeks ago, she got her latest assessment notice from the county: $59,800.

Roop was among nearly a thousand people who have thronged the county appraiser's office over the past few weeks, protesting assessments that have risen an average of 30 percent since the last appraisal in 1979.

As residents of one of Northern Virginia's most rapidly developing counties, Roop and her neighbors are finding themselves caught in a property tax crunch far worse than anything seen in the close-in Washington suburbs.

Driven upward by a growing demand for inexpensive housing among the county's rolling hills, assessments in Stafford are growing by leaps and bounds while those in other area jurisdictions are standing still or even declining. At the same time, the needs of an increasingly urban population have driven the county's property tax rate up by more than 50 percent since 1979, from 90 cents to $1.45 per $100 of assessed valuation, and many fear that the rate will only continue to climb.

Roop, a registered nurse at Mary Washington Hospital in Fredericksburg, is worried because the $579 property tax bill she paid in 1981 is likely to go up to at least $867 this year. "I think the assessments should be lowered; they're just too high," she said. "I think it's unfair, especially with the way the economy is today."

Roop said she and her husband, a self-employed mechanic, moved south from Alexandria in part to escape high property taxes. "It will be tight," she said.

Others residents, like 84-year-old Pearl Beckham, are more philosophical about the rising costs. Beckham bought 17 acres of land in east Stafford County in 1918, and has seen taxes go up reguarly ever since.

"I paid $2 a year tax on that land when I got it. Last year I paid $197 tax on it," she said. "There's no use to get mad about it. They just keep raising it up and raising it up anyway."

Stafford County officials defend the county's rising tax bills, saying that more money is needed to provide services for a county population that has more than doubled over the past 20 years, from 17,000 residents in 1960 to 42,000 in 1982. That rate of growth is expected to continue for the next 20 years, with a population of 81,000 projected for the year 2000.

"Say it costs the county $1,500 for each school child, or $4,500 for each family. The taxes aren't that high," says county revenue commissioner George L. Gordon Jr. "We're now in a growth area. Values and taxes always go up in a growth area."

Property appraisers Kenneth W. Strickler and S. Russell Bailey say assessments will continue to climb as Washington-area workers keep coming to Stafford in search of affordable housing.

"Unfortunately, taxes follow people. A lot of people have moved down here to get away from taxes," Bailey said. "And for their tax dollar they're expecting the same services they had before, from a county that's still mostly rural."

That kind of reasoning doesn't offer much comfort to Georgeana Layton, a neighbor of Roop's who says her tax dollars have done little to maintain roads and clean up a swampy area near her house.

"We're paying much too much for nothing," Layton said. "I don't know why people are coming here from Prince William County. They're paying the same amount of taxes and with the gas crunch they might as well stay where they are."

The county's appraisers said they do not know how many appraisals will be changed. "All we can do is try to explain the criterion we used," Bailey said. "We feel some compassion, but what are we going to do?"