The 205R16 was the standard tyre for all the 90s of that period. Rostyles were never fitted to the 110s because they didn’t meet the axle loadings required (neither did the OE 205R16 tyres). Early Rostyles were known for cracking and splitting, although later ones were improved. 7.50s were an option on all 90s, including the V8 CSW, but if they were ordered they all came on the plain 5.5” rims. The Rostyle/7.50 combination was never officially offered by Land Rover because the tyre’s weight limit exceeds that of the rim so it was deemed as unnecessary, although of course it would work and there is no reason why you shouldn’t go down that route on your 90 – a lot of people do.
Rostyle wheels fitted with 205R16 tyres were standard fitment on Range Rovers until 1985. From 1986 all UK Range Rovers were fitted with the three spoke alloys as standard. It is common folklore that Land rover had a such surplus of old stock Rostyle/205R16 combinations from 1986 they chose to ‘lose’ them on the 90 V8 CSW and to distinguish it as the premium 90 model. They actually stayed on the options list for the Defender 90 in the UK as late as 1995!