Q: Why can’t I connect to my Mikrotik router?
A: Mikrotik uses a version of OpenSSHd that uses an obsolete DH group exchange. ConnectBot does not support that at this time.
I’m using an Aladdin eToken PRO for several years to access SSH servers. Unfortunately these only support RSA keys.
Also there’s no common agreement on whether DSA or RSA is better. Since there’s no critical security issue in any of them, it would be wiser to let sysadmins decide which one to trust.