The semifinal form must be :
As roma
Leverkusen
Sevilla
And juventus
But things looks like in unexpected way. So it might be between feyenoord , leverkusen , manchester united and juventus , sepite sporting cp doing well away and then will play at home in the second leg , i still think juventus can handle it, as roma might be the one i doubt can get through.
Your these selections are not bad at all but after watching many matches in last few years I still believe predicting about UEFA results are never been easy because we can have any surprise in any game in first leg matches we have all matches very close with Leverkusen and Manchester United held by opponents and ended with draw matches and Juventus and Feyenoord having 1 - 0 lead which mean all eight teams still in competition and anyone can go through into last four.
But, as you have your four teams I am personally feeling we will have Juventus, Leverkusen, Manchester United and Feyenoord into last four because these are still having quality and performance for winning their respective matches.
I'm not sure about Leverkusen after the game we sew in the first leg I won't be surprised anymore if I see Saint Gilloise winning the second leg against Leverkusen because of the first half of the game since I didn't know Saint Gilloise I was not expecting to see this perfect performance from them but they were performing perfectly and there is a chance to Saint Gilloise to win the second leg and surprise us which can be tempting to bet on Saint Gilloise.