Rogers variant: model RM820 with pentaband UMTS and North American LTE. For 3G/4G, band support includes: AWS (T-Mobile USA), 850 & 1900MHz (AT&T), and 900 & 2100MHz (rest-of-world).
AT&T variant: also model RM820 but for UMTS probably has AWS (and also 900MHz) disabled, so no T-Mobile 3G/4G...