Restaurants in northern NJ serving passover style dinners
Most diners, steakhouses and fish markets will offer options of bread/leavened free meals. You can always just get a salad or grilled protein with a baked potato. Some may even have matza available. I know one Panera that offered Matza instead of the bread. If you are looking for more than that, there are fewer options as many kosher restaurants close for the week since the burden of cleaning to please everyone for Passover is often too great.
As for Rosa Mexicano, the "Passover Menu" is a loose interpretation of K for P. It follows a Sephard variation and uses corn and rice.
390 Hackensack Ave, Hackensack, NJ 07601
I believe the 2 traditional Passover dinner evenings were last Monday and Tuesday. You'll have to wait until next year...
No reason to be guilty, either, unless your Grandmother is calling you and provoking you. Do you observe the Sabbath? No driving on Saturday? No turning the lights on or off?
You didn't specify if you're strictly Kosher or just trying to keep Pesach, but I'm sure you can find good eats at Eppes Essen (Livingston), The Ritz Diner (across the street from EE), or Irving's (Rt 10 in E. Hanover)...
105 E Mount Pleasant Ave, Livingston, NJ 07039
72 E Mount Pleasant Ave, Livingston, NJ 07039