At the back of my house they get the sun at Sunrise till very late in the afternoon. There I planted "Orange Nectar" "Mary Rose" "La Sevillana" and "Gold Bunny" all Standards they do not perform well at all, apart from the first flush there have hardly been any flowers on them the past six months, La Sevillana is a crimsom and hates the sun it gets white streaks on all the petals so they all will be getting moved to a shadier spot this Autumn.

I also have a climber "White Iceburg" on the chook yard fence in the sun, same thing not many flowers at all. I know this is not good rose weather here in Brissie with the humidity then the rain, but I honestly think too much sun is not the best for them where I live, others may not agree with me especially from down south.

You could try them if they dont grow too well, put them in pots and maybe you can move them around I would anything a go. Good luck whatever you do......MM

But if you are on the border you may have sandy soil so forget the gypsum and add more compost, most soils will grow roses so you should not have much trouble. Happy Gardening ....MM.