The aim of conversational speech processing is to analyze human conversations in natural settings. It finds numerous applications in personality traits identification, speech therapy, speaker identification and verification, speech emotion detection, and speaker diarization. However, large-scale annotated datasets required for feature extraction and conversational model training only exist for a handful of languages (e.g. English, Mandarin, and French) as the gathering, cleaning, and annotation of such datasets is tedious, time-consuming, and expensive. We propose two scalable, language-agnostic algorithms for automatically generating multi-speaker, variable-length, spontaneous conversations. These algorithms synthesize conversations using existing non-conversational speech datasets. We also contribute the resulting datasets (283 hours, 50 speakers). As a comparison, we also gathered the first spontaneous conversational dataset for Urdu (24 hours, 212 speakers) from public talk shows. Using speaker diarization as an example, we evaluate our datasets and report the first baseline diarization error rates (DER) for Urdu (25% for synthetic dataset-based models, and 29% for natural conversations). Our conversational speech generation technique allows training speaker diarization pipelines without the need for preparing huge conversational repositories.