TC aux. Who where they?

[Peroni]

There's a list I beleive on the Adamklissi monument.

I can tell you about the Batavian Cohorts though...

Cohors I Batavorum (Milliaria Pia Fidelis Civium Romanorum):

The ‘Civium Romanorum’ or ‘Citizens of Rome’ suffix, giving the entire unit full citizen status was granted during the Dacian campaigns of the emperor Trajan (AD102 – 106) . The diploma from Raetia (RMD-02, 00086 dated December AD113) found at Regensburg (Castra Regina) details the full honorific titles granted to the cohort, as does another diploma from Pannonia Superior, provenance unknown. (AE 1997, 01782 = RMD-04, 00223 dated to 3 May 112).
The cohort was then transferred back to Solva in Upper Pannonia and later Dacia Porolissensis.

Ala Batavorum Milliaria Civium Romanorum Pia Fidelis

this unit is attested for the Dacian Wars, (AE 1987 00829) and were garrisoned there in Romania (IDR 03-04-79b to IDR 03-04-82).

Cohors II Batavorum Milliaria Equitata
Also fought in Trajan’s Dacian campaigns.

Cohors IX Batavorum Milliaria
From Vindolanda as a milliaria unit. It then departed in 105 to fight in the last part of the Dacian Wars. There is evidence for the unit in Dacia Inferior and Moesia Inferior until 112CE. At Buridava in Romania, tiles have been found with the inscription CIXB dated to this time