The Roth decision was refined in 1973 in Miller v. California. While similar, the standard is slightly different:
The basic guidelines for the trier of fact must be: (a) whether 'the average person, applying contemporary community standards would find that the work, taken as a whole, appeals to the prurient interest, (b) whether the work depicts or describes, in a patently offensive way, sexual conduct specifically defined by the applicable state law; and (c) whether the work, taken as a whole, lacks serious literary, artistic, political, or scientific value.
But again, that applies to obscenity, not pornography. Pornography is protected speech in the US, obscenity is not.
A bit off topic in deciding the line between erotic and pornographic.