No, there is not a limit to the amount that you can convert from a Traditional IRA to a Roth IRA in a given year. It is not considered a rollover, but it is a conversion.
You will need to know the basis of the Traditional IRA since that portion of the conversion will not be taxable.
As you enter the Form 1099-R reporting the Traditional IRA distribution you will see some follow-up questions that ask what you did with the money. You should answer that you 'moved the money to another retirement account' and 'did a combination of rolling over, converting, or cashing out the money'. Then you will see a box to enter the amount that was converted to the Roth IRA.
Another follow-up question will ask about whether there were any nondeductible contributions made to the Traditional IRA in order to calculate the taxable amount of the conversion.