Hello, I'm Keith and happy to help you with your question.
Business Asset Roll over Relief in respect of Capital Gains Tax as it is called is limited to premises occupied the purpose of your trade or business. You should have a look at HMRC Help Sheet 290. Unfortunately this makes it clear that the premises must be occupied and used as described although a building used for holiday lettings does comply.
I fear that your rented property does not fall within the rules. I would be inclined to write to your tax office for advice on this matter, but I do not hold out much hope. The Help Sheet gives numerous examples of roll over relief, but none for rented property save holiday lettings and a combined shop with living accommodation over example.