3/10 10:00 AM PT -- As if the enormous rock wasn't enough romance ... A-Rod made sure the bedroom was ready for a "she said yes" celebration. Check out the bed of roses, and yeah ... he gave us a glimpse of J Lo too.

Somebody cue up some Marvin Gaye!!!

Alex Rodriguez popped the question, Jennifer Lopez said yes, and they both shared their exciting news ... at the same time!!!

J Lo and A-Rod are engaged after dating for a little more than 2 years and announced it on Instagram with simultaneous posts Saturday night. They each shared a pic of him holding her hand while showing off her MASSIVE new rock.

Jennifer captioned hers with heart emojis, and Alex captioned his "she said yes" (followed by a heart emoji). A-Rod also shared a screenshot of the definition of "Soulmate" by Bianca Sparacino on his IG story hours beforehand ... a signal something big was coming.

It reads ... "A soulmate isn't someone who completes you. No, a soulmate is someone who inspires you to complete yourself. A soulmate is someone who loves you with so much conviction, and so much heart, that it is nearly impossible to doubt just how capable you are of becoming exactly who you have always wanted to be."

No word on any wedding plans yet, but if the engagement ring is an indicator ... no expense will be spared.

Congrats!