As the cost of lobster rolls continues to rise, one local restaurant chain is ensuring the quintessential New England handheld remains affordable without sacrificing its quality. Burtons Grill & Bar is selling the brand’s premium lobster rolls for just $29 throughout the summer. From now until Aug. 31, Burtons’ diners can get their hands on a chilled Maine-style or warm Connecticut-style at all its locations, including its eight Massachusetts restaurants.