What is the role of advisor in writing a PhD thesis?
The general responsibilities and authority of the PhD supervisor will be quite different in different universities, especially in different countries. It may even be very different form one department to another.

I attended University of Toronto, Physics. In my case, my supervisor was very involved both formally and informally. He would visit my desk at least 2 times per week and ask how things were going. He would make helpful suggestions, ask useful questions that showed he understood, and would keep asking questions until he did. He was OK with me coming to his desk any time. 

He suggested the topic. He gave useful hints on how to start. He answered a ton of my questions. He told me when it was time to write up some thing like a synopsis or submit some form. And he negotiated with the university to set dates for various exams, submission of various things, and who would be on my exam committee. 

One of my profs described his experience at another university. His prof was a "big name in physics." He gave a talk at the department about his research. The BNIP was in the front row, asking useful and interesting questions, suggesting interesting ways the work could be applied to interesting questions, etc. 

Then at the end of the talk the BNIP said to him "That was a very good presentation. Who is your PhD supervisor?" "... You are, Dr. BNIP."  "Oh! Oh! In that case, come by my office tomorrow and we'll set up your oral exam."

The thing to do is try to estimate if you are in fact getting what you need to complete your degree. As long as it's getting done then don't worry too much. 

Check with other grad students what they are doing.

You might need to ask the support staff at your university if you are missing doing anything like submitting forms or things. They will know because they do the actual work most of the time. Your department head's secretary or the secretary of the head of grad studies. You should ask them if you are missing anything.