You can use as much of your Roth IRA funds as you want for a home purchase. The issue is how much of the distribution from the Roth IRA is tax free and how much is subject to penalty.
You always take out your original Roth IRA contributions tax- and penalty-free without having to have any exceptions to the early-distribution penalty. These are distributed from your Roth IRAs first. Only if you will be dipping into the investment earnings that were accrued in your Roth IRAs would you have a need to use the first-time homebuyer's exception on up to the first $10,000 of earnings (or taxable Roth conversions that have not met the 5-year holding period). If it's been more than 5 years since the beginning of the year for which you first made a Roth IRA contribution, the amount of earnings to which you apply the first-time homebuyer's exception will also be income that is excludible from taxable income. Whatever amount is includible in income will be subject to ordinary income tax.
Just be aware of the requirements to be a first-time homebuyer and that if any of the Roth money is in a designated Roth account in a qualified retirement plan like a 401(k) that money would first have to be rolled over to a Roth IRA and then distributed from the Roth IRA for any of the above to apply. See IRS Pub 590-B on regarding the definition of a first-time homebuyer.
There are no provisions in the tax code that allow the IRS to waive early-distribution penalties for circumstances other that those explicitly defined in the tax code: https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-tax-on-early-distri...
