Simple Password Utility
My critique is mostly on the crypto.


Never invent your own crypto. It's difficult to do correctly, and there are already good libraries for this sort of thing. See sinatra-authentication or bcrypt-ruby.
rand() is not a cryptographically secure random number generator, so it's a poor choice for use in crypto. Also see point #1.
Your password salting is incorrect. The salt must be mixed with the password before hashing, not after. Also see point #1.
Why append the length_of_salt_and_hash? That seems pointless.
Why append salt + hashed_pass? These are usually stored as separate fields in a database record.
Avoid magic numbers like 61 in your code. What does Roger Maris have to do with this? It's unclear and redundant that this 61 refers to the length of the string on the next line.
You ask for "better or more verbose." Those are often opposite goals. More verbose code means more code to read and more code to maintain. (That does not mean you should prefer cryptic one-liners.)