To determine my ROTH IRA contribution limit do I use the new Unemployment Compensation Exclusion MAGI or MAGI that includes my unemployment compensation?

It depends,  If your AGI is $150,000 or less and the unemployment compensation up to $10,200 was excluded from your income, you may have to add it back to calculate Modified Adjusted Gross Income.  

Modified Adjusted Gross Income is the adjusted gross income with any tax-exempt interest income and certain deductions added back such as:

• Any deductions you took for IRA contributions and taxable Social Security payments
• Excluded foreign income5
• Interest from EE savings bonds used to pay for higher education expenses
• Losses from a partnership
• Passive income or loss
• Rental losses

Duplicate question already answered here:

https://ttlc.intuit.com/community/retirement/discussion/what-magi-value-do-i-use-to-find-my-roth-ira-contribution-limit-the-new-unemployment-compensation/01/2178098