Simple question, thanks for your time. I am just wondering what freedoms did the most basic of citizens have (when there was an emperor, not the senate). I don't really need an explanation; a list might suffice.
Wikipedia answers the question rather well, and I would vote to close except that OP asked about "freedoms", not about rights, and the wikipedia article emphasizes rights. @Tyler correctly highlights the fact that "Freedom" is a slippery concept. I cannot make the argument briefly, but I'd argue that what Montesquieu meant by freedom is different from what Hobbes meant, and both are different from what Jefferson meant, and none of them would agree with any definition posed after the invention of the welfare state. The modern (let's say post 15th century) definition of freedom has something to do with an individual's right to self-determination. That definition is null and void in Rome, where every action must take place in a network of competing obligations to class, gens, tribe, family, political party, etc. All of which is merely prelude to point out that the points I'll make below are open to argument.
I would argue that the most significant freedom that a Roman citizen had was that in theory they lived in a state ruled by law, rather than by autocracy. Every other state was ruled by some form of autocracy where "law" was an extension of the ruler's whim, and today's law could be tomorrow's treason.
Rome had a set of laws that were published on tablets that were available for review by every Roman citizen. (Let's leave aside for the moment the level of literacy, and also leave aside the notion that writing the laws and executing the laws are very different functions; those two problems are present in every state that is ruled by law).
Of course OP narrowed the scope of the question to the Imperial period; One could argue that Augustus tried to limit himself to some form of constitutional imperial hybrid, and perhaps continue the argument up through Claudius. Shortly after that the state degenerates into autocracy (with brief interludes). At that point I would no longer argue that "freedom" as defined during the Republic existed. One might argue that there was a degree of freedom created because custom and tradition imposed limits on the power of the Empire, but that freedom dwindled with every generation.
During the Imperial period, Roman citizens had the "freedom" of being part of the institution of empire - meaning that their rights and privileges were stronger/more authoritative/more likely to be respected than non-citizens (either slaves or foreigners).
[Aside: I started to make the claim that Romans had access to a judiciary; a Roman citizen had access to a court and could obtain a legal settlement, and could appeal the settlement, but the case and the appeal were not strictly based on law. I think the Roman judiciary is sufficiently different in character from either the British common law or the French judiciary that it is a disservice to compare them. I would have to be a far better scholar of both Roman Imperial history and of jurisprudential history to analyze and explain that claim. Update: My shoddy legal scholarship is buttressed by @oldcat, who informs me that Roman courts were
I suppose one could argue that they had "freedom from want", because of the grain dole, but I would have trouble making that argument with a straight face.