How can I get the license group 'G' (UK), last one!?

I have passed & hold all the rest but this one is elusive! Been to a lot of driving schools and asked about this. It's a roadroller catagory.
Answers:
www.dvla.gov.uk
I thought if you have past your test group G it is automatic, that you are allowed to drive a roadroller

Age 17 for small road rollers with metal or hard rollers. They must not be steam powered, weigh more than 11.69 tonnes or be made for carrying loads

Road Rollers Category G Min age 21 Any weight above 11.69 tonnes and steam powered.

A road roller is not a public vehicle and cannot be driven on public roads except for highway repairs.

Anybody can drive a road roller with a licence over the age 21, with it being a vehicle for highway repairs,
Thats why G is not showing on licence
bbc.co.uk/cbeebies/funandgames

B-b The Bu-lder (Yahoo won't let me type in the full name!!)

PMSL!

No idea really. Sorry.
Try contacing the DVLA or road construction companies.
contact the DVLA