Here's an interesting bit of fan theory I found online - it's in a Tumblr post, so it's easier for me to cut 'n paste the assorted pictures and text rather than putting a link for people to follow. Not claiming these ideas are my own:
jay-oracle:
So everyone’s talking about Rose/Pearl’s relationship and such, but I’d like to point out another interesting thing about this episode.
When Pearl makes holo-rose, she’s recreating the scene. She repeats it, word for word. Every expression Rose made, every shift of a curl. And as we all know, Pearl is an extreme perfectionist. She wouldn’t change a detail of this scene.
So what am I getting at? Pearl’s posture.
Pearl is down on one knee. Heck, she’s GENUFLECTING. Everything about her posture and expression illustrates extreme respect, and this is before they are even allies in battle.
My next point is Rose’s Flag. It could very well be a revolution flag meant to represent the crystal gems, it’s true. But take a look at it. It’s 100% rose quartz. None of the other gems are represented on it in any way. Don’t you think it would be a little out of character for Rose, who’s all about loving everyone and everything, to make their flag all about her? It seems a little vain for this selfless gem we’ve been shown.
So here’s my theory; Rose Quartz was gem Royalty. Or at least held a very high rank. All of the gems respect her unconditionally (beyond that, they all seem positively enamored with her) she has whole armories, she has an insignia on a FLAG. It would make sense that Rose would be an incredibly important gem. As far as we know Rose was the only gem with healing abilities. Even Lapis Lazuli seemes shocked to hear that Steven had healing powers. Rose could have held the life of her entire species in her hands, which would make her pretty damn important. So if the gems do come back to earth, what will we learn about Rose, and who she was before she chose earth?
stevemanrp:
What if Rose Quartz isn’t actually Quartz?
Look at her gem. and well,
this is the pinkest piece of gemstone cut rose quartz i could find on a cursory search. See how its smokey and not really “pink” like Rose’s gem?
Well, I have a gem that matches it much better.
This is a rose
diamond.