I respect your feelings on the matter but you don’t have the right to impose your spiritual needs on everyone else. When I go to Mass, it is the only time I get out of my home. The rest of the time, I’m stuck inside and don’t see anyone except when my priest comes and I can have the Sacrament of Reconciliation. Much as he would like to stay and chat with me, Father is so busy that he simply cannot spare the time, it’s asking a lot of him to come over for confession as it is.
When I get into the church, I like to say hello to people and get the chance to chat. If 20 minutes or more is spent doing the Rosary before Mass, you are forcing people to stay quiet. They may not be preparing to receive Jesus simply because you are saying the Rosary. They may actually spend the time wanting to strangle those who took away their only social contact. It is also very difficult for many people to make it for Mass as it is, relying on other people, such as a neighbour. For some sick people, the hour for Sunday Mass is difficult enough to sit for, asking ninety minutes will be impossible. So that means that people will be arriving as Rosary is going on, hardly a prayerful experience.
You don’t mention what is happening before the Mass, when does the previous Mass (if there is one) finish? There needs to be a certain amount of time to allow people to leave and others to come in, it could be impossible. Also, what happens if you overrun, should Mass be delayed?
I think you have to accept that in this case, your priest is being reasonable in refusing to change something that the majority of his flock have no problem with and may actively look forward to. The happiness of having had people talk to me, to be able to share something I’ve been waiting all week to tell someone can be excellent preperation to receive Jesus, rather than feeling depressed and lonely I feel part of a community. For example, two weeks ago yesterday, my sister gave birth to a little boy, after a 40-hour + labour and an emergency caesarian. That made me an auntie for the first time, something that gave me immense joy. However, as it was the early hours of Monday, I had to wait six days to tell someone! The renewal of that joy was a perfect preparation to receive Christ.