Hi,
I think it possible you could use a roller; how much needs to be painted.
https://www.zinsseruk.com/product/bulls-eye-1-2-3/
This Zinsser paint would be ideal as a base/sealing coat.
I like using a Pelican seen here;
https://www.screwfix.com/p/wooster-pelican-hand-held-paint-scuttle-0-95ltr/7132g
Using one of these you then can use both brush and roller with ease so if you experience problems reaching with the roller then quickly use the brush and then roll over; I can highly recommend using one of these Pelicans; I've used mine with brush and roller to give the bungalow exterior paintwork a comprehensive makeover and I didn't skimp on paint I used top quality Benjamin Moore paint which is American but now available in the UK. It's a few years since I did the exterior painting and it's still like new unlike every other paint I've used which quickly failed due to our dire climate.
Here's the rear of our bungalow painted using the Pelican; for the siding I quickly went over with the brush to get into tight places then used the roller; it was incredibly quick.
Even the framework was firstly touched in by brush then finished with roller.
Here's another option if you can afford it; spray painting; I gave our master bedroom a comprehensive makeover but for speed I bought an Apollo spray outfit which did a superb job on the woodork. for the bare walls and coffered ceiling inner panels I used the Pelican.
After installing the coffered ceiling and wall wainscot panelling my arms had suffered enough hence I used the sprayer.
Our front room nearing completion; I made the wooden fireplace mantle but sprayed this before installing it; the wall paneling needed over 300' of softwood moulding which I made; I used the Pelican again but this time with a 2" wide roller to get into the spaces; the walls again using the Pelican but with roller after cutting in by brush.
The Pelican has cheap disposable liners but I found it easy enough to wash the liner; brush and roller out having used water based paint; I'd bought a dozen Pelican liners but only used the original and now this original liner is still used for treating our garden huts. Using a roller is definitely quicker than using a brush. I also used the Pelican when I gave our front room a comprehensive makeover as seen.
Good luck.
Kind regards, Colin.