Philipp Peter Roos art links 

Fine Arts Museums of San Francisco
Shepherd Boy with Sheep and Goats

Hermitage Museum, Saint Petersburg, Russia
Landscape with a Grotto
Landscape with a Waterfall

J. Paul Getty Museum, Los Angeles
Descent from the Cross, 1696

Kunsthistorisches Museum Databank, Vienna (in German)  

Louvre Museum Graphic Art Database, Paris (in French)   NEW!  

Museum of Fine Arts, Boston  
Paintings collection online

Courtauld Institute of Art, London, UK
Landscape with ruin and man loading a donkey

Harvard University Art Museums, Massachusetts   NEW!

Le Musée Ingres, Montauban, France (in French)   NEW!  
Click on the artist name, then on the artwork title to view the work

Palais Fesch Musée des Beaux-Arts, Ajaccio, France (in French)  

Princeton University Art Museum, New Jersey   NEW!

State Museums of Florence Digital Archive, Italy

 
National Art Databases and Museum Inventories:

Joconde Database of French Museum Collections (in French)  

UK National Inventory of Continental European Paintings (NICE)   NEW!

 

Philipp Peter Roos in the Web Gallery of Art  

Wikimedia Commons Image Database  

Bildindex der Kunst und Architektur (in German)  
(a welcome screen is displayed for a couple of seconds before the search results appear)

Ciudad de la Pintura (in Spanish)  

State Hermitage Museum Unofficial Site   NEW!

 

UK Government Art Collection

 

Grove Dictionary of Art Online (excerpt)  

Union List of Artist Names (Getty Museum)  
Reference sheet with basic information about the artist and pointers to other references.

Oxford Dictionary of Art (eNotes)   NEW!