Use of a personal vehicle for business is covered in chapter 4 of publication 463.
https://www.irs.gov/pub/irs-pdf/p463.pdf
You can't take anything for the roadside assistance plan if you use the standard mileage rate method.
You may be able to include roadside assistance if you use the actual expense method (it's not specifically included or excluded). But, you would have to allocate the cost to the vehicle used for managing rental properties. That means that in addition to tracking all the vehicle mileage and expenses for the vehicle in question, you would have to track the total yearly mileage for all vehicles covered by the roadside assistance plan, so you could properly allocate the cost.
See also these prior discussions
https://ttlc.intuit.com/community/investments-and-rental-properties/discussion/rental-property-trave...
https://turbotax.intuit.com/tax-tips/small-business-taxes/business-use-of-vehicles/L6hi0zzzh
In short, this is listed as a vehicle expense on schedule E. To use the standard mileage rate, you report the miles driven to each property. The standard mileage rate includes allowances for fuel, repairs, insurance, maintenance, depreciation, and everything else. The only thing you can add is tolls and parking.
To use the actual expense method, you must track all your vehicle expenses for the year, including insurance, repairs, maintenance, fuel, depreciation. You must also track all your vehicle mileage for the year, both business and personal. You then deduct a percentage of total expenses equal to the percentage of business miles. And yes, this means that if you have a $1000 breakdown on the way to work on one of your properties, but your total yearly vehicle mileage is only 20% for managing the rental, you only deduct 20% of the cost. For a service contract covering multiple vehicles, you will have to know the total of all vehicle miles driven. For example, suppose vehicle A is used 12,000 miles during the year, of which 6,000 is for managing rentals. The assistance plan also covers vehicle B (8000 total miles per year) and vehicle C (2000 miles per year). 54% of the assistance plan is allocable to vehicle A. Then, you would deduct 50% of that allocation (27% net deduction) because vehicle A was used 50% for business.
On Schedule E, you would further allocate your miles to each property, but the final deduction will be based on total miles driven for work as a percentage of total miles driven for all purposes.
The standard mileage rate is often more lucrative than the actual expense method, and requires much less record keeping.
