Eccentricity and orbital period for all confirmed exoplanets (grey dots in the main panel), those that have been observed in transit (regardless of whether they were discovered by that method; orange dots) and those that are Roman-accessible in the optimistic CGI configuration, with P_access > 25% and V < 7 mag (green dots). We only consider those planets for which e is known and P can be derived as explained in Sect. 4.1. The black line shows the limit between short- and long-period exoplanets (P = 382.3 days) as defined in Kipping (2013) (see Sect. 4.1.2). Top panel: P distribution of all confirmed exoplanets (grey), those observed in transit (orange line), and those that are Roman-accessible (semi-transparent green). Right panel: normalized distribution of e such that it shows the relative frequency instead of the total count of planets. The same colour code applies as for the top panel. The green bars are semi-transparent (so that the grey distribution underneath can also be seen), so that the overall graph becomes either darker or lighter green depending on whether the two histograms overlap. For reference, we include the eccentricity for the subsets of short- and long-period exoplanets in Kipping (2013; red and blue lines, respectively).