That's how it's supposed to work. From the Marriott Rewards Elite Rollover Nights page:
"It’s easy to make every night count:
*Silver member nights in excess of 10, Gold member nights in excess of 50 and Platinum member nights in excess of 75 all carry forward to the next year."
MR customer Support: 1-801-468-4000 (8:15am - 9:00pm, Monday - Friday, US Eastern time)
1-800-450 4442 (toll-free, 24 hours/7 days per week) Please note: the toll free number is an automated line.
Like foxglove states, the best advice is to just call Rewards and get the scoop straight from them. We have found that being right is overrated, so even if you were "supposed" to get them, if you didn't - you didn't, so protect yourself, just in case.
Now here's a possible scenario which might explain you not having any rollover nights; If at the beginning of 2013 you rolled over, let's say 20 nights from 2012, and you 'earned' 40 nights in 2013 (for your total of 60), then you would maintain your Gold status, but have no rollover nights, because rollover nights only roll over once (and no, you can't ask them to roll over ten of your 2013, butt in bed nights, instead ).
So give them a call and see what's what. Good luck.
I ran into a similar issue. I rolled over 55 nights last year and the little bar chart showed with over 125 days for the year so I just assumed they would rollover the extra 50 but that is not how it works. The customer service rep was nice and was willing to help me get platinum status again but I won't need the help since I'll be traveling every week for next 6 months. However I do think Marriot Rewards needs to find a better way to display the rollover nights and in property nights because the logical conclusion of the bar chart is anything over you last tier would roll over!!!