This is a really exquisitely painted bowl and having studied the quality and style closely I am happy to attribute this to the hand of William Billingsley, who was arguabley the greatest painter of roses on porcelain.

The colour of the roses is wonderful, and the colours used in the leaves, very sophisticated and well observed.  The style of painting is very similar to water colour, where the application of the enamels is very thin and totally transparent allowing the porcelain to shine through.  This makes every brush stroke visible.

The control needed to make such fine and accurate lines and create what are no less than tiny portraits of roses is quite astounding.  The softness of the petals, small tears at the edge of a petal, or an insect bite, captured with tiny movements of the brush.

To make this feat even more virtuosic, the roses are painted across a change in direction of the porcelain, and are painted partly on the rim and partly in the dip of the bowl.  Please study the pictures carefully to see this, some of the later pictures show the bowl at different angles so that you can see more clearly the contour of the surface.

Very few people were capable of this level of control.  An intimate study and intuitive understanding of the anatomy of the flower, as well as highly controlled and practiced muscle memory were needed to paint this bowl, the result of years of study and practice.

Painted with a loose band of roses, thistles and shamrocks, within gilt line borders, and measuring 17.9 cm diam, impressed crown and BFB mark and printed Flight, Barr and Barr mark "Manufacturers to their Majesties and the Prince Regent".

A plate of this design is also illustrated in W. D. John WILLIAM BILLINGSLEY illustration 69D, which is included in the pictures for this item.  

A very similar plate in this design also sold at Bonhams 2006, see the link below.

https://www.bonhams.com/auctions/13952/lot/245/

Footnotes
Billingsley arrived in Worcester in 1808 and worked as a painter until at least 1810-1811. From about this time until his departure in 1813, Billingsley's talents were put to use in improving the Worcester body, although he probably continued to paint intermittently.

This bowl must have been painted shortly before his departure, just at the time of the change in the name of the partnership from Barr, Flight and Barr to Flight, Barr and Barr. The border composed of the symbols of the Union may indicate that the plate was a trial for a Royal service

Makers marks:
Flight Barr and Barr 

Diameter:
17.9 cm

Weight:
209 g

Age:
208 years

Condition:
Very good

Maker:
Flight Barr and Barr, decoration attributed to William Billingsley