How does a Roman polytheist worship today?
The Roman state no longer exists, and for a wide variety of reasons we in Templum Deorum are absolutely not interested in trying to resurrect the Roman bureaucracy or the public side of Roman religion (see section 1). The state festivals were not even the level of religion most dear to the average Roman. Every Roman family honoured its familial spirits and patron deities within the privacy of their own home. This is an excellent focus on which to reconstruct Roman religion, for all it requires is a some space in a domestic environment called a lararium, along with a few tools and supplies (see: what is a lararium?) Romans also formed many private associations to honour a common deity, and this can be replicated when enough followers are within driving distance of each other.
