Have the Disney World app open and be sure you are logged in while you're outside the park. There will be Rise of the Resistance boarding group information when you open the app, click on the link, select the parties who you want boarding passes for, hit the next button. Once you enter the park refresh the page or go back/forward and you should be able to get a boarding group pass as soon as you enter. Keep in mind you need to have all parties who want to ride with you on your account and in the park before you can add everyone. When I was there waiting to get in the park, I noticed many people didn't know anything about this - they couldn't remember their passwords to log in either and weren't promptly being sent a password resent E-mail. I felt bad for them.
Monday I was there at 5:20 AM waiting in shoulder-to-shoulder crowd which was extremely scary to me and seemed like a fire hazard or disaster waiting to happen. This was not my first attempt and my anxiety made me leave times before, for me, that was very difficult. Disney opened Studios at 6:30 AM, a half hour before park opening at 7 AM. I was able to get a boarding group of 30 as soon as I entered, walked on Tower of Terror and very small wait with a continuously moving queue for Toy Story Mania. My boarding group for RotR was called around 10ish, but had a lot of down time/broke ... etc. I got a free Dasani water. It was a good experience, I enjoyed the virtual queue, but I find it a bit cumbersome for those staying on property being that Disney transportation isn't running early enough for guests to get to Studios at 5 AM to ensure a boarding pass. I'm not so sure if the attraction is worth all that honestly for 3 cool preshows, a Stormtrooper photo op (I'd prefer Boba Fett/Han Solo in carbonite/Jabba the Hutt), and a 3 minute ride that relates to the new movies (I'm an original 3 fan). However, I'm very happy I was sucked into the hype. haha. It was cool.