You can install as much fire precautions as you want - the RRO doesn't limit you - you could have a small lock up shop and put an L1 fire alarm in, Oxy-Reduct, a 50Kg wheeled extinguisher, emergency floodlights, etc
I think you are saying:
A building has an Internet cafe on ground floor with 2 occupied bed-sits on the first floor. Does the RRO apply & if so would putting FD30S fire doors on the bed sits satisfy the minimum necessary fire precautions?
Does it apply - it could as Kurnal says
Are the doors enough - Unlikely on their own
More info on the property would help, such as age, whether the bedsits are off a stair with a separate entrance to the cafe, has the 1st floor always been flats/bedsits or did it used to be the retail units 1st floor and much more