Hi everybody,
As you can guess from the title I have a problem connecting two Mikrotik using SSH with RSA inside Winbox.
I did a lot of tests and I try to summarize them.

I generated the RSA key pair with PuTTY Key Generator:
Type of key generated: RSA
Number of bits in generated key: 2048

I exported both the public key and the private key (I tried to export the private key both with and without the password but nothing changed).
I exported the private key in both PPK and OpenSSH format.

I configured the two Mikrotiks with the same "admin" account and "12345678" password.
In the first Mikrotik (client) I imported the private key for the admin user:
In the second Mikrotik (server) I imported the public key for the admin user:
If I connect to the "server" from a PC using PuTTY and the PPK key I am able to connect.
Instead, when I connect to the "server" from the Mikrotik "client" I am immediately disconnected.
If I try to connect from Tools->Telnet->SSH the window opens and immediately says "Disconnected".
If I try to connect from terminal:
after a few seconds I get the message "Welcome back!".

have you tried as below?
Ser@fin

Yes, using the password it works but I would like to use it with RSA without a password because I would like to use ssh-exec.

which version do you use?

7.8 is OK, 7.9 is broken, 7.10 is broken when import new private key, 7.11beta7 corrected .

Downgrade to 7.8, clear all private key, and re-import private key, and then upgrade to 7.10.2, will work.

You're great!
I'm using 7.10.2 and it doesn't work but using 7.8 it's ok!
Thank you very much!!!