Principal/Senior Machine Learning Scientist - Search and Discovery

Every day, tens of millions of people come to Roblox to explore, create, play, learn, and connect with friends in 3D immersive digital experiences– all created by our global community of developers and creators. At Roblox, we’re building the tools and platform that empower our community to bring any experience that they can imagine to life. Our vision is to reimagine the way people come together, from anywhere in the world, and on any device. We’re on a mission to connect a billion people with optimism and civility, and looking for amazing talent to help us get there. A career at Roblox means you’ll be working to shape the future of human interaction, solving unique technical challenges at scale, and helping to create safer, more civil shared experiences for everyone. With Roblox’s daily active users growing at a record pace, we are seeking experienced machine learning researchers who thrive on solving complex challenges and designing scalable, ground breaking solutions. In this role, you will innovate on LLMs, VLMs, autoregressive models, or other large models for user understanding, content understanding, recommendation, and agentic search. Your work will lay the foundation for personalizing user experiences, enhancing engagement and retention, and driving growth within the creator ecosystem. In search and discovery, you will contribute to the core systems that enable users to discover and interact with experiences across Roblox. On Search, that work spans the end-to-end user search journey, covering query suggestions, autocomplete, and retrieval and ranking. These systems drive exploration and engagement across all surfaces, helping users find relevant and exciting content. Looking ahead, our team aims to innovate further by developing auto-generated summaries, images, and videos from experience content to improve discoverability and inspire user exploration. Our mission is to connect a billion users with the best content and connections at the right time, tackling diverse challenges in advertising, search, and discovery at an unprecedented scale. Join us and play a pivotal role in shaping the future of Roblox’s search and discovery. You Will: Design and implement the machine learning solutions that power agentic search and discovery systems to drive Roblox content distribution. Design and implement large scale recommendation models. In this role, you will innovate on LLMs, VLMs, autoregressive models, or other large models for query understanding, user understanding, content understanding, recommendation, and agentic search. Design eval and post-training loops - SFT, preference optimization, and RL - for ranking, query understanding, and agentic systems. Balance researching new technologies with a practical approach to integrate research efforts into the Roblox products. Collaborate with other teams within Roblox to make sure we are building products with a community first approach. Communicate with the industry and communities where applicable and be ambassador for Roblox. You have: You have 7+ (for principal) or 4+ (for senior) years of experience designing and building scalable machine learning solutions. Experienced with transformer based model training, inference, and product integration. Break down product requirements into iterative deliverable stages. Depth in recommendation, search retrieval and ranking, or LLM post-training and agentic systems is a plus. You have a BS, MS, or PhD in Computer Science or a related discipline or equivalent experience. You have initiated and facilitated challenging technical decisions across multiple teams and organizations. While deeply technical, you always start with the needs of the user, whether they are Roblox users or internal engineers. A creative and strategic approach to solving hard problems. You simplify the complex. You bring in fresh ideas from new places. For roles that are based at our headquarters in San Mateo, CA: The starting base pay for this position is as shown below. The actual base pay is dependent upon a variety of job-related factors such as professional background, training, work experience, location, business needs and market demand. Therefore, in some circumstances, the actual salary could fall outside of this expected range. This pay range is subject to change and may be modified in the future. All full-time employees are also eligible for equity compensation and for benefits as described on this page . Annual Salary Range $278,530 — $345,040 USD Roles that are based in an office are onsite Tuesday, Wednesday, and Thursday, with optional presence on Monday and Friday (unless otherwise noted). Roblox provides equal employment opportunities to all employees and applicants for employment and prohibits discrimination and harassment of any type without regard to race, color, religion, age, sex, national origin, disability status, genetics, protected veteran status, sexual orientation, gender identity or expression, or any other characteristic protected by federal, state or local laws. Roblox also provides reasonable accommodations to candidates with qualifying disabilities or religious beliefs during the recruiting process. For US based roles only, please note the Company may not be able to employ candidates for this role who have United States work authorization related to certain U.S. visa categories, or support future H-1B sponsorship at this time.