I have a Mother of pearl rose bush that has a large bunch of red branches and leaves in the top middle of the bush. This is the second season for the bush and I didn't see anything like this last year. I don't know whether to cut it out or wait and see what happens.
Red Branches and Leaves in Rose Bush
I highly recommend that you leave it be and keep an eye on it! That nice dark red growth and leaves is the sign of new growth for the rosebush most of the time and a sign that it is happy and healthy. You should start to see buds form at the ends of the new growth soon if they have not started forming tiny buds already. If the red colored growth is more mottled looking and the new growth as a torn or broom looking shape to it, well, that spells trouble and good be rose rosette disease which is caused by a nasty incurable virus. Here is a link to an article about rose rosette disease for you but I would imagine that it is just the new good growth: https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-rosette-disease.htm