Yes. Speak to the concierge. Ask about length-of-stay tickets if you are staying a number of days that is different from the the standrad ticket options.
I don't think you get any special deal by buying at the hotel, just convenience.
If you buy tickets at the HRH you pay full price but there are a few benefits. Show your ticket at any Universal Park gift shop and get a 20 percent discount. The HRH tickets will also get you coupons for 10% off at various City Walk restaurants and some 2 for 1 drink coupons for City Walk also. We got coupons for a free souvenir (sp?) with the purchase of a dinner at NBA Cafe. We didn't have time to stop in the gift shop the night we ate there but went back the next day - showed the coupon with no proof we ate there and get free NBA City basketball pens. These perks did save us a few dollars.
We got our 3 day passes at the HRH & were able to get the AAA discount. They also gave us some cards for additional discounts at CityWalk. I would go for a 2 or 3 day pass instead of length of stay. We only ended up using 2 of the 3 days. With FOTL by staying at HRH we were able to see everything in 2 days, even though the parks were closing at 7pm when we were there.