As yoozer18 says in the comment, your question appears to be contradictory in that you say "rollover" and then "back into the account". A rollover is when you move money from one account to another.
But assuming you mean a rollover, the simple answer is that the amount that you deposit in the new account is a rollover. The amount that you keep is a withdrawal. If you take $25k out of account A and deposit $20k to account B, then you have a $20k rollover and a $5k withdrawal.
You'll commonly hear the financial advice that it is advantageous to have your financial institution transfer any money directly. If you do that, you are not subject to any tax. If you withdraw the money and then deposit it somewhere else, the old account holder is required to withhold tax. You then have to come up with the cash from somewhere else to replace this money when you deposit to the new account, or the withheld tax will be considered a withdrawal subject to tax.