what argument could slovaks, Romanians and poles make in support to a nationalist uprising against austrian empire?

Answer: 1) germanization (German as a state/official language), 2) political rights were limited for them, 3) nationalism.

Explanation: Austro-Hungarian empire was multinational empire. In terms of population majority was non-German speaking, but official language was German and later German/Hungarian. German-speaking Austrians were "Herrenvolk" (reigning people) which was in fact minority. At the same time, all these smaller (majority Slavic) nations were inspired by German nationalism and started fighting for their national rights and their national identity. It means that the empire was full of national conflict ... especially in the end of the 19th century.