Other firms in the top 10 include Nike, John Lewis and HMV - with companies offering career progression, flexible working and perks dominating a list compiled by job site Indeed, based on employees' reviews.
The top firms are well known for treating workers well, such as sharing profits or paying for professional exams.
Bill Richards, managing director of Indeed, said: "While the need to earn a salary is the imperative that makes us go to work, it's far from the only criteria we judge work on.
"Benefits and workplace flexibility play an important role in workplace happiness, but they're not the key determinants of what makes an organisation great. For most employees, feeling valued, a positive company culture and quality management matter more.
"Having fun, feeling like you're having an impact and seeing that impact extend beyond the company to the world - those are the things that make a workplace really special."
Daniel Perkins, global employer brand manager at Rolls-Royce, said: "At Rolls-Royce, we recognise that our people are our power.
"We employ over 23,000 people in the UK across a huge variety of roles, functions and business areas.
"This includes over 1,000 apprentices and graduates and we work to create an environment where every employee can reach their full potential, encouraging diversity, engagement and development."
The top 10 - in order - was made up of Rolls-Royce, Nike, John Lewis, HMV, Kumon, Marriott Vacations, KPMG, Siemens AG, GAME and GlaxoSmithKline.