Was actually speaking with RR folks yesterday re this. The F130 is a RR BR725 which is itself a variant of the BR710. The BR725 is already used on platforms such as the Gulfstream G650.
Comparing engines:
P&W TF33-P-3 as already used on B-52H
Length: 142.3 in (3,610 mm)
Diameter: 53 in (1,300 mm)
Dry weight: 4,605 lb (2,089 kg)
Thrust: 17,000 lbf (75.62 kN)
RR F130 as proposed for new B-52?
Length: 129.8 in (3,297 mm)
Diameter: 50 in (1,270 mm)
Dry weight: 3,605 lb (1,635.2 kg )
Thrust: 17,000 lbf (75.62 kN)
So same thrust but in a slightly smaller, lighter package.