Senior Machine Learning Engineer, Search Assistant

Roku•San Jose, CA

23h•$361,300 - $510,000•Hybrid

About The Position

Roku's Entertainment Assistant team is building the next generation of AI-powered discovery experiences across the platform through text, voice, and conversational interactions. The team owns the end-to-end discovery stack, including language understanding, GenAI-powered experiences, retrieval systems, ML-driven ranking and personalization, and whole-page optimization. We focus on delivering highly personalized and context-aware entertainment experiences while balancing user engagement, long-term retention, and monetization across Roku surfaces. Our systems leverage modern ML and GenAI techniques, including LLMs, reinforcement learning, multi-objective optimization, and agentic workflows, to help millions of users effortlessly discover content they love. We are looking for a Senior Machine Learning Tech Lead to drive ranking and personalization for Roku’s next-generation entertainment assistant across the platform. This role sits at the intersection of Search, Recommendations, Conversational Discovery, and Monetization, with the goal of delivering highly engaging, personalized, and context-aware entertainment experiences. You will lead the development of large-scale ML systems that optimize for multiple objectives including user engagement, long-term retention, satisfaction, and monetization. The role requires strong technical leadership, product intuition, and the ability to balance user experience with business impact across diverse discovery surfaces.

Requirements

8+ years of industry experience (or PhD with 5+ years) applying ML at scale in search, recommendation, ads, personalization, or related domains
Strong expertise in ranking systems, recommendation systems, retrieval, personalization, and multi-objective optimization
Experience building large-scale ML systems leveraging deep learning, sequence models, LLMs, reinforcement learning, or bandit frameworks
Strong product intuition and experience optimizing user engagement, retention, and monetization simultaneously
Proficiency in Python, Java, or Scala
Experience with distributed systems and ML infrastructure such as Spark, Airflow, streaming systems, feature stores, and cloud platforms
Strong technical leadership, system design, communication, and problem-solving skills
MS or PhD in Computer Science, Statistics, or a related field

Responsibilities

Lead the technical vision and roadmap for ranking, personalization, and recommendation systems powering Roku’s entertainment assistant
Develop and deploy state-of-the-art ML models using deep learning, transformers, LLMs, bandits, reinforcement learning, and causal inference techniques
Build multi-objective optimization systems balancing engagement, retention, relevance, and monetization goals
Drive innovation in conversational discovery, contextual recommendations, and personalized content experiences across the platform
Design, run, and analyze online A/B experiments tied to key product and business KPIs
Architect scalable ML systems, feature platforms, and data pipelines supporting rapid experimentation and long-term growth
Mentor engineers and provide technical leadership across cross-functional initiatives involving engineering, product, UX, and analytics teams