RADIO OBSERVATIONS OF GRB AFTERGLOWS WITH THE VLA AND ALMA CAN ADDRESS SEVERAL FUNDAMENTAL OPEN QUESTIONS IN GRB SCIENCE: (1) THE COMPOSITION OF THE RELATIVISTIC EJECTA THROUGH OBSERVATIONS OF THE REVERSE SHOCK RADIO EMISSION (2) THE EXPLOSION PROPERTIES OF SHORT GRBS WITH IMPLICATIONS FOR RADIO COUNTERPARTS OF ADVANCED LIGO SOURCES AND (3) WHETHER HIGH-REDSHIFT GRBS FORM A DISTINCT POPULATION THAT MAY POINT TO POP III MASSIVE STAR PROGENITORS. HERE WE PROPOSE TO ADDRESS THESE QUESTIONS USING ON-GOING JVLA AND NEW ALMA PROGRAMS WHICH REPRESENT THE MOST COMPREHENSIVE RADIO/MILLIMETER VIEW OF SWIFT GRBS. THE PROPOSAL TAKES ADVANTAGE OF THE UNPARALLELED SENSITIVITY OF VLA AND ALMA AND BUILDS ON OUR LONG-TERM SUCCESS IN RADIO STUDIES OF GRBS.