RSA is specifically designed to allow you to share that public key, so yes, you can publish it. This is pretty similar to how x.509 (and SSL) with RSA certificates works.
Before publishing the file, actually look at it; the only things that need to be in there are the keyword "ssh-rsa" and the base64-encoded key. You may want to keep it to that (I believe this is the default now).
This is true whether or not the key has a passphrase. A passphrase encrypts the private key and does not affect the public key.
Ensure, as always, that your key is sufficiently entropic and large. If it is generated by a broken PRNG it might be predictable. However, publishing this doesn't present much additional risk, since if the keyspace is that small an attacker could simply try with all the keys in the enumerated keyspace until they get the right one.
I suggest using a 4096-bit key (specify
-b 4096), so that it will be more difficult than usual (the default is 2048) for someone to invert your public key into a private one. That is the only significant risk in doing this, and it isn't a very big one since the algorithm is specifically designed to make it impractical.