Roundcube 1.2.1 has been released. It's a bug fix release. These traditionally work fine by just renaming the last ebuild. Changelog: https://github.com/roundcube/roundcubemail/wiki/Changelog#release-121
Can confirm, just doing a `cp roundcube-1.2.{0,1}.ebuild` worked for me.
commit 079ff90450c6bd739208c3164d0c41d20917ba00 Author: Aaron W. Swenson <titanofold@gentoo.org> Date: Thu Sep 22 14:34:56 2016 -0400 mail-client/roundcube: Version Bump Version bump fixes bug 590608. RDEPEND updated for dev-php/PEAR-Crypt_GPG-1.4.0 fixing bug 584728. Keywords dropped for ~hppa, ~ppc, ~ppc64, and ~sparc due to requirement on >=dev-php/PEAR-Crypt_GPG-1.4.0. (Related bugs: 574264, 594824) Bugs: 584728, 590608 Package-Manager: portage-2.2.28