M.G. (Pat) Robertson, the religious talk show host, walked into a broadcast studio today and was inaugurated as chancellor of his own university -- a ceremony that was testimony to the growing power that diciples of the so-called "electronic church" have in Virginia.

Speaking at dedication ceremonies for CBN University, a school named after his Christian Broadcasting Network, Robertson predicted such colleges ultimately would turn the nation away from a government "run by public opinion polls" toward one governed by Christian principles.

Dedication of the $34.1 million colonial-style university and broadcasting complex was the latest example of what has become a growing and politically significant movement that reaches millions of Americans. Robertson's own $55 million network now has 163 television affiliates in all 50 states and boasts of reaching more cable TV subscribers than any other broadcasters in the world.

The dedication ceremony came a day after Robertson confirmed he is resigning from The Roundtable, a politically controversal church group based in Washington.

"My resignation. . .was appropriate in light of the confusion in the public mind as to my role in political matters," Robertson said in a statement.

The television evangelist, who founded his CBN operation in 1960 on assets of less than $70, lent his support two years ago to the unsuccessful Democratic Senate candidacy of a born-again Christian. Conley Phillips of Norfolk.

Robertson, the son of a former Virginia Democratic senator, was also active, along with Lynchburg evangelist Jerry Falwell, in April's Washington for Jesus rally on the Mall and a recent Dallas conference that attracted Ronald Reagan. Those events have been criticized by many main-line ministers for their right-wing overtones.

Robertson made no mention today of his decision to concentrate on religious matters. But he and other speakers here made it clear that they, unlike other religious broadcasters, believe that education should be an immediate priority. r

John R. Dellenback, director of the Peace Corps during the Ford administration and now president of the Christian College Consortium, told the audience of 400 educators and officials that schools like CBN University are "sorely needed. . .in this troubled and splintered world."

He argued that schools like Harvard, Columbia and Yale are no longer serving the religious education purposes for which they were founded. Saying that "faith, learning and living should be so intertwined that they're one and the same," Dellenback urged boosters of Robertson's university to help it produce "graduates who are first and principally followers of Christ."

The CBN center, a huge, cross-shaped brick structure with television studios at both wings, is richly adorned, with marble floors, antiques, religious paintings and sculptures and what the CBN officials call the most lavish broadcasting facilities outside of New York and Los Angeles. Aided by private donations and $15-a-month pledges from the 285,000 members of Robertson's show, "The 700 Club," CBN maintains a busy programming schedule and a telephone counseling service that handled more than 1 million calls last year.

The university, which is still seeking academic accreditation, opened its school of communications in 1978 and its school of education this fall. Future departments in fine arts, law, business administration and international relations -- as well as a hotel and shops -- are planned for the 347-acre complex, according to an aid, "as the Lord provides."