Three stars. Rated PG-13. 122 minutes. Denzel Washington delivers a performance for the ages in “Roman J. Israel, Esq.,” an appealing if ultimately frustrating urban thriller by Dan Gilroy. Three years ago, Gilroy made an impressive directorial debut with “Nightcrawler,” a moody evisceration of Los Angeles’ parasitic tabloid media culture. Here, he once again dives into unfamiliar regions of his city – in this case, its rapidly gentrifying downtown — to create a backdrop for his indelible title character, a progressive criminal defense attorney at war with his most cherished ideals. That battle is already well underway in “Roman J.