Spheno, thank you for correction on the dates (Indonesian state visit and the Olympic reception): i have amended that in my post.
Very little is known about the brooch but I am pretty certain the flowers aren't roses, so "Rose Gold Brooch" sounds a bit confusing to me, especially since Her Majesty has other similar gold brooches which actually
are roses. I had also not seen the wonderful entry at the HMJV and did not base my name on that article, but simply on what seems to be (to me) the best actual description of the jewel itself until and unless we have more information on its provenance.
In regards to the brooch worn at the Investiture ceremony, I have to disagree. The few pictures that are available aren't the clearest, but having zoomed them to maximum, I just can't see a flower basket of any sorts, and certainly not the multi-gem Flower Basket Brooch. To me, it looks like the brooch the Queen is wearing is a flower one with two blossoms, each with a single stone in the middle. I have attached a magnified (and unfortunately, very unclear) picture of the brooch from the Investiture. The only brooch (again, in my opinion) from the Queen's collection that matches the jewel she is wearing is the White and Pink Gold Flower Brooch (or Rose Gold Brooch).
Of course, you are totally welcome to have a different opinion.