I removed the sod last year and now I am waiting for the temperatures to raise so I can seed. From what I am reading Early in April is the best time here in Toronto (5a) Do I need to rototill before seeding? I know it would have been better to do this before winter but the stars did not align for me
Take a golf ball and throw it onto the soil surface. If it bounces off and rolls down an incline you are in trouble. If it buries itself into the surface about halfway then that is good. April sounds about right, watch for a period of warm but showery weather.
For rototilling it really depends on the quality of the soil as it is right now. The benefits would be that fluffing up the soil would make it easier for grass seed roots to penetrate and also for rain and irrigation water to go straight down rather than sideways float washing all of your seed into a thick mass at the bottom of an incline.
First, take a sample of the soil and decide whether you have a heavy clay, light sand, or a nice loamy mix. You can do this with a mason jar test, and there are many existing reports on how this is done. Then at least when talking to others about the issue you can say what the soil profile is. When taking the sample with spade or trowel, if it is hard to push the trowel into the soil surface that is an early indication that just putting down seed will be a waste of time and effort.
If it is easy to get the sample for the test, take a rake and see how easy it is to get it to bite into the top half inch or so of the soil surface. When you put down the seed it will need to be covered a little to get it to stay in place long enough to root and get started. There are various ways to do this, easiest is to cover with existing soil, alternatives are to cover with a layer of something on top such as chopped straw or a light loam soil mix.