A recent survey by The Roper Organization shows that a growing number of people who say they understand the mission of federal regulatory agencies believe that the Food and Drug Administration, the Environmental Protection Agency and the Consumer Product Safety Commission aren't doing enough to protect the public.

At the same time, the survey indicated that people who say individual government agencies are overregulating are consistently outnumbered by those who say the agencies are too lax.

The results indicate that the Reagan administration, which has accused regulatory agencies of overburdening the nation's citizens and businesses, may be out of step with the public on this issue.

The findings are based on a nationwide, face-to-face survey of 2,000 people conducted by The Roper Organization during the week of Aug. 15, shortly after Vice President Bush unveiled the second "hit list" of regulations to be reviewed and possibly relaxed. A similar survey involving most of the same regulatory agencies was conducted in August, 1979.

The agencies whose mission was most widely understood by the public were FDA (80 percent of the respondents said they had a clear idea of its mission), EPA (66 percent) and the CPSC (59 percent).

Those with least public recognition were the Securities and Exchange Commission (30 percent), and the Federal Trade Commission (39 percent.)

When the figures were adjusted to exclude people who said they didn't understand the agencies' missions, the results showed:

* A wide divergence of opinion about the work of the EPA and the Occupational Safety and Health Administration. In the case of the EPA, 37 percent said it did too little regulating while another 25 percent said it did too much. Only 33 percent said it did the right amount.

* In OSHA's case, 37 percent said it did "the right amount" of regulating. The others divided evenly between those saying it did too much and those saying it did too little. Responses were polarized on income and educational lines: higher-income and better-educated people were more likely to say OSHA did too much.

* The number of people who approved FDA's level of regulatory activity increased slightly between 1979 and 1981; those saying FDA does too much were outnumbered 2 to 1 by those saying it does too little.

* The Federal Aviation Administration received a greater approval rating--68 percent--than the other agencies in the poll. While a growing number of people said the FAA does too much, they were outnumbered nearly 2 to 1 by those saying it does too little.

(Burns Roper, head of the organization, pointed out that the 1979 poll was taken three months after a DC10 lost an engine and crashed in Chicago, killing 273 people; there have been no major fatal crashes in two years.)

* Forty-one percent of those surveyed said the CPSC wasn't doing enough (up from 36 percent), while 12 percent said it did too much.