Napoleon Bonaparte certainly played a significant role in the French Revolution. Whether or not he helped it or was responsible for its end depends greatly on your point of view.

In a practical manner, he certainly helped its cause in 1795 when he commanded forces in Paris during the brief War in the Vendée. This attempted reestablishment of power by royalist forces threatened to undo the republican efforts of the Revolution. Napoleon's successful repulsion of the royalists led to his instant fame and promotion to major general.

Throughout the later years of the 1790s, Napoleon victoriously commanded the French army against the other major powers of Europe. In this way, he helped preserve the French Revolution: the other European monarchies, such as Austria and Great Britain, hoped to see the Bourbon monarchy restored.

However, Napoleon's role in preserving or ending the French Revolution grows murky in 1799. In November of that year, he returned to a very unstable France. Once there, Napoleon participated in the Coup of 19 Brumaire, which overthrew the Directory. Napoleon replaced the Directory as head of a three-man consul, making him the most powerful person in France. Two years later, he seized further power through a constitutional amendment naming him consul for life. In 1804, he went beyond even this by crowning himself emperor of France.

If you look at it one way, Napoleon preserved the French Revolution by restoring stability to France after years of chaos and dysfunction. If he had not done so, it is quite possible that the French Republic would have crumbled and all the desires of the revolutionaries would have been for naught. By taking power, he was able to safeguard the newly won rights of the Third Estate. On the other hand, by essentially making himself no different than a monarch, Napoleon defeated the democratic ideals of the Revolution by turning France into yet another monarchy.