A participant is limited to two active roles in the congress and to only one paper presentation. You can be a paper presenter in the new session or a discussant, but only one other role.
Yes, individuals can submit an individual paper presentation and participate in the congress as a workshop/roundtable participant. Note however that a participant is limited to only two roles in the congress and that the role of organizer does not count towards the limit of two roles.
A workshop/roundtable participant is not considered a paper presenter since these sessions do not have formal paper presentations. A workshop/roundtable participation does count as an active role.
An individual can only present one paper. If your name appears as a co-author, this counts as your paper presentation.