Channel 7 drew nearly 1,500 protest calls Thursday night from viewers who missed the eagerly fifth episode of Alex Haley's "Roots" because the station made a last minute time change.

"Roots" originally had been scheduled for 8 p.m. in order to make way for a 9 p.m. basketball game between Maryland and North Carolina State. The one-hour network program normally would have started at 10 p.m.

Last week, the station learned it would have to move the game back to 8 p.m., and "Roots" to 7. But by then, Sunday TV supplements published by both Washington dailies had gone to press with the 8 p.m. time listed.

Both newspapers, in their Thursday editions, noted the earlier start for "Roots". In addition, the station made continuing announcements, beginning with the completion of the Wednesday night segment of "Roots" of the 7 p.m. Thursday starting time.

At one point in the evening the WMAL switchboard was so overladed that Channel 8 (CBS) began to get dozens of angry phone calls in the apparent hope the protests would be relayed to the ABC affiliate.

One middle-aged viewer who missed the segment showed up at the Connecticut Avenue studios of WMAL to protest. He had to be shooed away by police when he began annoying station personnel on their way to work.

Channel 7 officials yesterday made a vain attempt to get ABC's permission to re-run the one-hour Thursday night episode just prior to last night's two-hour version of "Roots," in order for viewers to catch up.

But long-standing contractual obligations between ABC and "Roots" producers and actors permit only one netwerk re-run the hit. ABC apparently plans to re-run the entire Haley drama about the black American experience later this year.

Meanwhile, ABC figures indicate that both the fourth and fifth episodes of Alex Haley's story of the American Negro experience continued to make TV audience history.

National Nielsen figures indicate that the Wednesday night episode was seen by 78 million viewers, making it the sixth most widely viewed TV show ever.

Roots Three and Two have already established themselves as the third and fifth most popular, while the premiere episode now ranks ninth on the all-time list.

Ovenight Nielsens in New York, Los Angeles and Chicago indicate Thursday nights fifth episode continued to score in record viewer numbers.

Praise for the program continued to pour in from educators and black leaders from around the country.

Two minor incidents of racial trouble apparently resulting from the reaction of black high school youths to "Roots" presentation of slavery were reported by Associated Press to have occurred in schools in Detroit and Harrisburg, Pa.

Several white youths in each were attacked by black youths, without serious injury, according to AP.