Oud or Aoud is an oil distilled from Agarwood. It's most commonly used in perfume in the Middle East.
Real Oud is very much an acquired taste. The smell can be medicinal, sharp, and unpleasant to many noses. Katie Puckrick once described it as "air du Chernobyl".
I have never smelled the Trish Mc'Evoy perfume, but as an offering from a cosmetics company my guess would be that it doesn't have very much real oud in it at all, despite the price. I don't know that for sure though.
If you want to try a perfume that mixes roses and oud really beautifully then Black Aoud by Montale would be a good starting point. The rose is dark and rich, and the oud is distinct, particularly in the opening. If you prefer something lighter then Montale also do a White Aoud, which includes some rose in the composition. Neither will be cheap though.
Honestly? If you want nice perfume with real ingredients in it then it's going to cost you. You might be able to buy perfume for £25.00 that has roses and/or oud in the title, but I can guarantee you it won't have any real rose or oud in it. These ingredients cost a lot of money, and real, beautifully composed perfume costs a lot of money to produce. Save up and buy yourself something really good would be my advice.
HTH