Before he turned 40, Roland G. Fryer Jr. had earned tenure at Harvard, received a MacArthur “genius” grant and won the most prestigious award for young American economists. He stoked a national debate by concluding that police officers show no bias in the shootings of black men.  But his rapid ascent has taken a troubling turn as Harvard officials review a university investigator’s conclusion that Dr. Fryer fostered a work environment hostile to women, one filled with sexual talk and bullying. The findings, reviewed by The New York Times, found that Dr. Fryer had engaged in “unwelcome conduct of a sexual nature” toward four women who worked in the Harvard-affiliated research lab he created.