What to write in first mail to a role-model researcher for PhD position?
This is a wrong approach and attitude. The whole thing will result in disappointment 99% of a time, because: 

Your Work Should Impresses People Not Your Emails: If you think there is golden secret rule, that make your email irresistible to those people you want to impress then you be wrong. All you need is a good set of achievements. 

Finding a Role-Model Without Knowledge: Whatever key points you might think that highlight a good researcher might be wrong because you did not achieved a good sense of research yourself. You might think, well he/she done this or that, and he/she might even rightfully impresses you; however, without knowledge of a field, finding a role-model to collaborate with is wrong. 

High Maintenance Supervisors are Worst For PhD Students: Good or bad, you need to make your PhD an impressive achievement, and not your supervisor(s). Now, lets assume that your assumption is right and he/she is the God in that field. These people are mostly are worst supervisors, because they have no time to spend on you. While you might ask him/her about a topic, you think he/she has the mental power and will to answer you? He/she is running around to that class/conference/journal or book deadline/new faculty member interviews and on and on. 

Conclusion

Don't waste your time chasing "role-models" while looking for PhD position. Find a supervisor that has time to spend on you. Someone that is always around to help his/her students. If you go with a "rock star" supervisor, then you most likely will be disappointed as he/she has no time to guide you through your PhD.