If you are asking yourself this question, then the answer is probably yes. It may seem like an easy thing to walk on a roof, but if you are not experienced with negotiating different pitches, and if there is any question at all about the roof's ability to handle the weight you are adding, do not attempt to climb on your own roof.
Shingles that have slipped out of place or those that are loose will always pose a threat to your safety while on the roof. It is very easy to step on a loose shingle that will take your feet out from under you increasing the chance that you will slide off the roof. The older your roof is, the riskier it becomes.
If your home has a roof leak that you see inside, your roof decking is already being damaged. As shingles are installed, the nails penetrate the wood. If water is added to that mix, the decking can deteriorate from the inside out. This leads to weak spots that can literally collapse as you step on them, causing a risk of falling, even death. Trained roofers know how to walk on a roof, testing their steps before they take them to ensure that the roof can handle the weight they are about to place on it.
It takes special training to walk or negotiate steep roof planes and it is never a good idea for anyone without this training to attempt to walk on a steep roof. The fall risk is simply not worth anything you need to accomplish, and this should only be left to trained professional roofers.