Never Look A Gift Horse In The Mouth
All the lies you find...All the truth you see...
Parallels, instructions, adding and removing. Can we fill in the blanks? Well, if one thing is for certain, there is more than meets the eye with some of these paintings. I'm not sure I can provide the answer but I believe I can help fill in the blanks.
It seems apparent if we are to fill anything in the Roanoke painting it would be the bubbles. The +/- symbols can provide some instruction but how do we know what needs to be added or removed with any level of certainty? It's actually quite simple. Three bubbles, one of which is already filled to point us in the right direction. The fairy is holding this bubble high. Perhaps, an offering or gift instructing us what we need to do? There are three constants across all paintings. Birth flower, birth stone, and month item. These items were critical to establishing the themes to the twelve puzzles as we have discussed here. They also appear to need manipulated in this case. Add an item to the right side, remove one from the left side, as instructed by the plus/minus signs. From the left we remove the watch so it must be added to the right. The gem would now be added to the left. This leaves us with the below.

The blanks have been filled. Now, can you make sense of them?
A special thank you to Chris and Phil for the work they put in prior to me even looking at this hint. Chris continued to mention the watch is being released which helped spur this idea for me. I knew the watch needed actioned and the carnation inside the bubble sealed it. Also, after I proposed removing the gem, Phil was quick to point out the minus symbol directly above the gem. So obvious after the fact! I'll let them add more of their thoughts in the comments.
Hope to have more for you all soon and till then...The gift you gave...Is gonna last forever...