Tazza were probably used for burning incense:
From an excavation
Replica in use at Newcastle
They don't tend to be as big as those from Chesters.
And a quick outline of what they are about:
Tazza: An Overview by Ray M. McBride
[ ...] initial thoughts from an ongoing study of the tazza, a small carinated bowl easily recognizable by the frill or piecrust decoration around the rim and on the carination. The vessel sits on a pedestal, which can take a variety of forms from long, wide, hollow and decorated. I considered past theories of function, demonstrating that lamps or incense burners were their most likely purpose. As to why the incense is being burnt, we can best assume it is for ritual reasons. The tazze appears in Britain in the Claudian period, with the Roman army. It seems to have formed an integral, if small, part of the repertoire of ceramic vessels, made and used by the military. The manufacturing of tazze clearly took place at the legionary kilns of the fortresses of Holt, Caerleon and York. This form follows the military on their campaigns throughout Britannia and into Caledonia. Its use passed from the military to the civilian population until the demise of its use in the third century.