When we refer to the "Rosette Cloud", we're talking about a typical SaaS cloud-based web API. The Rosette Cloud supports the majority of functions of the SDK as the Cloud uses the SDK code base. The Cloud is unable to support stateful and user-customized features - mainly Name Indexes (to disambiguate against a custom curated list of names, rather than the simple pairwise matching the Cloud is limited to) and model training -- our entity extractor can be trained against a dataset/model of your own in the SDK, but not in the Cloud. However, the Cloud contains features including Sentiment, Similar Terms, Topics, and Categorization, which are not currently implemented in the SDKs.
A newly-available product, really a "third flavor" of our text analysis suite, is "Rosette Enterprise". Users can run their own web server with all the same functions as the Rosette Cloud, but in an on premise model. This solves cloud security worries and allows customization (models/indexes) as needed.
Rosette Enterprise can be easily customized to fit into the system you need on-premise -- please ask us if you have any questions. We have an experienced team ready to help integrate Rosette Enterprise into your environment.