1. Yes Dovecot is running and it's ok with mail clients programs and SOgo too

2. maillog report this:
May 30 02:43:42 82 roundcube: <os4nt3g7> IMAP Error: Login failed for postmaster@xxxx.it from 79.46.207.34. Empty sting (127.0.0.1:143) in /var/www/roundcubemail-1.2.0/program/lib/Roundcube/rcube_imap.php on line 193 (POST /mail/?_taskion=login)
May 30 02:43:42 82 roundcube: PHP Fatal error:  Uncaught exception 'Exception' with message 'DateTime::__construct(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone.' in /var/www/roundcubemail-1.2.0/program/lib/Roundcube/rcube_user.php:491#012Stack trace:#012#0 /var/www/roundcubemail-1.2.0/program/lib/Roundcube/rcube_user.php(491): DateTime->__construct('now')#012#1 /var/www/roundcubemail-1.2.0/program/include/rcmail.php(619): rcube_user->failed_login()#012#2 /var/www/roundcubemail-1.2.0/index.php(109): rcmail->login('postmaster@astr...', 'xxxx', '127.0.0.1', true)#012#3 {main}#012  thrown in /var/www/roundcubemail-1.2.0/program/lib/Roundcube/rcube_user.php on line 491

This is my default_host param:

// IMAP
$config['default_host'] = '127.0.0.1';
$config['default_port'] = 143;
$config['imap_auth_type'] = 'LOGIN';
$config['imap_delimiter'] = '/';

I didn't change a bit

*) Did Roundcube work BEFORE you change ssl cert?
*) Please turn on debug mode in Dovecot mode, then try again. Show us FULL log related to this test in Dovecot log.
FYI: http://www.iredmail.org/docs/debug.dovecot.html

Seems caused by ssl cert.
Does it work if you revert SSL settings in Dovecot?

Try that now.
Nothing changed, same error after login page in roundcube, dovecot log said:

May 31 23:52:02 imap-login: Info: Disconnected (disconnected before greeting, waited 0 secs): user=<>, rip=127.0.0.1, lip=127.0.0.1, secured, session=<ZbASYio0MAB/AAAB>